Authorities in the US are investigating whether anyone helped an Afghan-born US citizen charged with carrying out bombings in New York and New Jersey.
Police in New York City also said they had not yet been cleared to speak to Ahmad Khan Rahami, 28, who was arrested on Monday after a shootout with police in Linden, New Jersey.
He has been charged with wounding 31 people in a Saturday night bombing in New York that investigators regard as terrorism.
The Federal Bureau of Investigation released a photo of two men who found a second, unexploded bomb they say Mr Rahami left in a piece of luggage in Manhattan's Chelsea neighborhood on Saturday night.
The two men, who took the bag but left the bomb on the street, are not suspects, officials said, adding that investigators want to interview them as witnesses.
"As far as whether he's a lone actor, that's still the path we are following but we are keeping all the options open," William Sweeney, the FBI's assistant director in New York, told a news conference.
Mr Rahami is also charged with planting bombs that went off in Seaside Park, New Jersey, and his hometown of Elizabeth, New Jersey, but did not injure anyone.
He faces charges from federal prosecutors in both states, with New York up first.
Federal prosecutors portrayed Mr Rahami, who came to the United States aged seven and became a naturalised citizen, as embracing militant Islamic views, begging for martyrdom and expressing outrage at the US "slaughter" of Muslim fighters in Afghanistan, Iraq, Syria and Palestine.
Prosecutors plan to move him to New York in the near future, from the Newark, New Jersey hospital where he is being treated for wounds sustained in the gunfight, once his medical condition allows, said Preet Bharara, the US attorney in Manhattan.
Mr Rahami's wife met with US law enforcement officials while in the United Arab Emirates and voluntarily gave a statement, a law enforcement official said. She was not in custody, the official said.
Mr Rahami's lawyer has asked for his first court appearance to be scheduled as soon as possible, even if it occurs in his hospital bed.
New York Police Commissioner James O'Neill said investigators had not yet received doctors' clearance to interview Mr Rahami, adding, "That may happen in the next 24 hours, pending the doctors' approval."
Federal prosecutors in New York noted that while they filed charges against Mr Rahami yesterday, he remains in the custody of state officials in New Jersey, who initially arrested him after Monday's gunfight.
Federal investigators were examining Mr Rahami's history of travel to Afghanistan and Pakistan, and looking for any evidence that he may have picked up radical views or trained in bomb-making on those trips.
They still are trying to find out whether he received any help in planning his attack or building the bombs.
