WASHINGTON — The homemade, pressure-cooker bombs used in the deadly Boston Marathon explosions were triggered by a remote detonator of the kind used in remote-control toys, U.S. officials said Wednesday.
The officials said investigators found pieces of the remote-control equipment among the debris and were analyzing them. Both U.S. officials are close to the ongoing investigation but spoke on condition of anonymity because they were not authorized to discuss it publicly.
One official described the detonator as “close-controlled” — meaning it had to be triggered within several blocks of the bombs.
A criminal complaint outlining federal charges against the surviving bombing suspect, Dzhokhar Tsarnaev, described him as holding a cellphone in his hand minutes before the first explosion.