Law enforcement sources told ABC News that Boston Marathon bombing suspect Dzhokhar Tsarnaev is awake and responding sporadically in writing to questions, according to a tweet by the network on Sunday.
Another tweet from ABC News reported that investigators are asking about other cell members and other unexploded bombs. Details about any answers have not been released.
Officials had previously said that he was not able to communicate yet.
Tsarnaev, 19, was captured Friday after being pulled bloody and wounded from a tarp-covered boat in a suburban Boston backyard.
He is being guarded by armed officers while he recovers at a Boston hospital, where he is in serious but stable condition. He reportedly suffered an injury to this throat, according to sources.
Tsarnaev's brother, 26-year-old Tamerlan Tsarnaev, was killed in a gun battle with police Friday.
Three people were killed and more than 180 injured when two bombs, apparently fashioned out of pressure cookers, exploded Monday about four hours into the race. The brothers are also suspected of killing an MIT police officer and severely injuring a transit officer.