IDAHO NATIONAL LAB -- 6:45 p.m. Thursday Update:

INL officials say the Jefferson Fire is 100 percent contained. This means firefighters have a fuel break around the entire fire. It continues to burn 170 square acres.

Firefighters will continue to watch hot spots and will work to fully extinguish the flames.

Commercial power was restored Thursday to the Materials and Fuels Complex. Monday, July 19 there is a mandatory safety meeting at 7 a.m. for MFC employees and subcontractors. The meeting will be about the status of the MFC buildings and equipment. It will be held in front of the MFC fire station.

There will also be a recording of the meeting. To hear that call 1-866-843-4681.

So far there's no confirmed cause of the fire.

4:50 p.m. Thursday Update:

The Jefferson Fire is close to being contained, INL officials said.

After Thursday afternoon's flyover, INL estimates the number of acres burned remains at 109,000.

Fire lines have been completed around the southeast side of the burned area. Crews continue to build perimeters around the north side and address the few remaining smoldering hot spots.

Tests were conducted to sample airborne radioactivity and conditions were normal.

Responders still do not know what exactly started the fire.

1 p.m. Thursday Update:

INL Fire Chief Eric Gosswiller told Local News 8 the Jefferson Fire was started by a human. The fire watch level on Tuesday was high, but still about two weeks away from critical. Gosswiller said they were surprised the fire happened when it did.

The chief said this is the largest fire the site has ever seen. It also spread faster than any other fire they've seen.

Flames at the site grew to lengths of up to 20 feet. Normally, flame lengths are about 12-15 feet.

It took INL firefighters about 10-15 minutes to respond to the fire. The fire remains at about 60 percent contained, but Gosswiller said he feels confident they will have it boxed in today.

Forest Service spokesman Lynn Ballard said fires like this are actually good for the land. It will help improve the habitat.

An update on burned acreage and containment numbers are expected later Thursday afternoon.

8:45 a.m. Thursday Update:

Firefighters have returned to the Jefferson Fire this morning. Fire lines have been completed on the fire’s east side and all but about five miles of its west side. Hot spots reside mainly on the north side of the fire.

Bulldozer crews at Sage Junction and at INL’s northeast end are working toward each other to complete the western fire line.

INL said they believe the fire is still about 60 percent contained. A fire is described as contained when a fuel break around the fire has been completed. This break may include natural barriers or manually and/or mechanically constructed lines.

A flyover Thursday morning is expected to give officials a better idea of how much acreage has burned and how contained the fire is.

9:00 p.m. Wednesday Update:

The Jefferson Fire is now 60 percent contained. The Bureau of Land Management and Idaho National Laboratory are pulling three of four crews off the fire for the night.

The fire is burning mostly sagebrush steppe, which is mostly shrubs and bunchgrasses.

Repair work on the downed utility lines to MFC and CITRC will begin Thursday.

Only essential INL employees who work at the MFC building will be called by their management to work. Three buses will leave the Willow Creek Building at 6:10 a.m.

6:00 p.m. Wednesday Update:

Responders to the fire at INL have dubbed it the "Jefferson Fire" because it started near Jefferson Boulevard.

The parts of the fire on INL property are estimated to be 40 percent contained and responders are monitoring for hot spots. Meanwhile, BLM is focusing on an active fire area on the northeast corner of the INL site, south of Mud Lake.

One firefighter has been injured while fighting the fire. He sprained his back.

3:45 p.m. Wednesday Update:

INL officials told Local News 8 the fire continues to burn.

Tuesday, it spread about 39 miles in four hours.

There is still no word on how the fire started or how much suppression efforts have cost.

12 p.m. Wednesday Update:

The fire has now burned about 109,000 acres or roughly 170 square miles, INL reports.

300 firefighters are fighting the fire on four fronts. Crews are focusing primarily on the north front between INL and State Highway 33. Also, on the west front, which is still on the INL reservation.

Fire crews are using bulldozers to build containment lines along Interstate 15 on the east side of the fire and from INL’s Central Facilities Area.

The Bureau of Land Management has dispatched 21 fire engines, a helicopter, five bulldozers, five air tankers and an air attack plane to fight the fire. INL has four bulldozers and seven fire engines on the scene.

A few INL structures have suffered minor damage.

INL said the cause of the fire is still unknown.

9:20 a.m. Wednesday Update:

Firefighters from INL, the Bureau of Land Management and other agencies continue to fight at the range fire at the lab’s desert site.

Fire observers are flying over the area this morning to assess the conditions. This will give officials a better idea of the fire's size and how much is contained.

9:45 p.m. Update:

According to INL, the fire has now burned approximately 30,000 acres or about 47 square miles.

INL is also asking that only essential MFC employees show up to work tomorrow. Most employees who work at the MFC are being advised to stay home.

Managers will contact those employees who are expected to show up to work tomorrow morning.

All other INL Employees should report to work as normal unless notified by a manager or supervisor.

Police have closed Interstate 15 from milepost 135 to 167 due to a lack of visibility. Flames from the INL fire have spread to the boarder of I-15.

State Highway 33 from milepost 33 to 59 is also closed to traffic

7 p.m. Update:

Power has been shut off to the utility lines feeding electricity to the Materials and Fuels Complex.

The fire is burning about 300 yards from the Transient Reactor Test facility near MFC.

The INL continues to report the fire is burning about 15,000 acres or the equivalent of 23 square miles. The fire is rapidly moving northeast toward Mud Lake.

All personnel at the Power Burst Facility, the Critical Infrastructure Test Range Complex and the Accelerator Center have been evacuated.

INL firefighters are responding to the fire. Four wildland fire units, two bulldozers and two water tenders are on scene. The Bureau of Land Management also has provided air support.

INL Officials said no company building is currently being threatened by the fire.

Chief Meteorologist Michael Coats reports sustained winds are more than 35 mph with gusts more than 45 mph in the area.

You can view live webcam images of the fire from Telegraph Hill or from Atomic City. If you select the "Telegraph Hill" Webcam, you must select the 'Telegraph Hill 2' option from the drop down menu.

You can see a loop of the fire's progression from the NOAA INL Weather Cam.

****Work status for INL’s Materials and Fuels Complex for Wednesday, July 14*****

Most employees at INL’s Materials and Fuels Complex should not report to work:

· Employees at the Materials and Fuels Complex will be on curtailment Wednesday, July 14. · Only essential employees will report to work at MFC Wednesday. · Essential employees will receive direct notification from their management to report to work. · Employees who are notified to work can either drive to work or catch an INL bus in the east parking lot of the Willow Creek Building in Idaho Falls. · The bus will leave the Willow Creek Building at 6:10 a.m. · The fire has burned an estimated 30,000 acres (nearly 47 square miles).