Federal authorities were at the apartment of deceased bombing suspect Tamerlan Tsarnaev on Sunday, executing a search warrant, an FBI spokeswoman said.
Amanda Cox said, "There is court-authorized law enforcement activity" at the home in Cambridge, Massachusetts, that Tsarnaev shared with his wife and young daughter.
Workers in white hazmat suits were at the apartment, CNN affiliate WCVB reported.
Cox said the search stopped for the day in the early afternoon. It was not immediately clear whether workers had taken anything from the home.
On Friday, a source briefed on the investigation said investigators found explosives residue in the small apartment.
It has turned up in at least three places, the source said: the kitchen table, the kitchen sink and the bathtub.
Tsarnaev's younger brother, Dzhokhar Tsarnaev, has said they built the bombs there, U.S. law enforcement officials briefed on the progress of the investigation said.
On Sunday, Tamerlan Tsarnaev's body remained at a funeral home, where his uncle said he was trying to deal with the logistics of readying the body for burial.
"I'm here to prepare his body, to wash it, shroud it, to prepare his body," Ruslan Tsarni said.
Tsarni said he was the only family member at the funeral home and had not had contact with Katherine Russell, Tamerlan's widow.
The funeral home owner, Peter Stefan, said he still has yet to find a cemetery willing to accept the body for burial.
A day earlier, he had said that if no gravesite is found, he plans to ask the government to find a grave.
Three cemeteries that Stefan contacted said they feared reprisals, but the funeral home owner said you can't pick and choose when it comes to a burial.
"This is what we do in a civilized society, regardless of the circumstances," Stefan said. "As I told some of them, at the immediate moment, you may fear (reprisal), but later on, when things calm down, people are going to resent you because you didn't do it."
Tsarnaev's death certificate has yet to be filed with the Boston city clerk, and there is no burial plot, according to the funeral home.
The city manager of Cambridge said Sunday he would not allow Tsarnaev to be buried in the city if requested by the funeral director or Tsarnaev's family.
"The difficult and stressful efforts of the citizens of the City of Cambridge to return to a peaceful life would be adversely impacted by the turmoil, protests, and widespread media presence at such an interment," City Manager Robert W. Healy said in a statement.
Tsarnaev died April 19 after he and his brother, Dzhokhar Tsarnaev, shot a university police officer to death, carjacked an SUV and hurled bombs at officers pursuing them, according to authorities.
A few days earlier -- April 15 -- he and his younger brother allegedly bombed the Boston Marathon, killing three and wounding more than 260.
CNN obtained a copy of Tamerlan Tsarnaev's death certificate, which lists the cause of death as "gunshot wounds of torso and extremities" and "blunt trauma to head and torso."
The document notes that Tsarnaev was shot by police and run over and dragged by a car. It lists the manner of death as homicide and notes that he was "DOA," or dead on arrival.
Authorities have said his younger brother may have run him over as they resisted arrest days after the marathon attacks.
Separately, 12 people remained hospitalized with bombing-related injuries on Saturday, according to a count by CNN. None was in serious condition.
Also, the frantic manhunt more than two weeks ago for the surviving bombing suspect drew the attention of gun rights advocates at their convention in Houston.
National Rifle Association Executive Vice President Wayne LaPierre said residents were "imprisoned" in their homes with no means to protect themselves while police searched for the younger Tsarnaev.