Authorities: Boston bombing suspect awake

Boston Marathon bombing suspect Dzhokhar Tsarnaev is awake and responding sporadically in writing to questions, authorities said. Investigators are asking about other cell members and other unexploded bombs, law enforcement sources told ABC News.

Previously officials said Tsarnaev was in no condition to be interrogated.

Tsarnaev, 19, is being treated at Beth Israel Deaconess Medical Center in Boston, where he is listed in serious but stable condition, with wounds to the neck and throat area, according to sources.

The bombing killed three, including a young boy, and wounded about 170. An MIT officer was allegedly killed by Tsarnaev and his brother Tamerlan and a Boston transit cop was badly wounded in a subsequent shootout.

The FBI is still collecting evidence from the Monday’s blast site, mainly from the sides of buildings and the bleachers.