Captured Boston Marathon bombing suspect Dzhokhar Tsarnaev is awake and "responding sporadically in writing to questions," according to news reports.
He is reportedly being asked "about other cell members and other unexploded bombs," law enforcement sources told ABC News on Sunday evening.
Authorities had been waiting to question Tsarnaev since they captured the Boston bombing suspect Friday night after a massive, city-wide manhunt.
The 19-year-old is accused of helping to carry out the attack which killed three people and wounded 180 others near the finish line of Monday's race.
Earlier Sunday, the FBI said Dzhokhar Tsarnaev remained in serious condition and sedated at the heavily-guarded Beth Israel Deaconess Medical Center.
Tsarnaev was brought by ambulance to the facility after he was captured in Watertown, Mass. He apparently suffered gunshot wounds to the neck and leg.
It was reported that a throat injury left him unable to speak - perhaps forever - but there have been conflicting accounts regarding this particular detail.
Tsarnaev's brother, Tamerlan, 26, the other suspect wanted by the FBI, was killed in a late-night firefight with police in Watertown the previous night.
Dzhokhar Tsarnaev managed to escape on foot, prompting a citywide lockdown as police conducted a house-by-house search for the alleged killer.
The Tsarnaev brothers, who were born in the former Russian territory known as Kyrgyzstan and are of Chechen descent, lived in Cambridge, Mass.
Dzhokhar became a naturalized American citizen just last year.
Under U.S. law, authorities have 72 hours after Tsarnaev's arrest to file a criminal complaint against him, which gives them until around 9 p.m. Monday.
When they do, he is expected to face terrorism charges.
"I hope that the U.S. attorney, Carmen Ortiz, takes him on the federal side and throws the book at him," Boston Mayor Thomas Menino said on ABC.
Richard Roper, a former U.S. District Attorney in the Northern District of Texas, said that Dzhokhar Tsarnaev could be charged in his hospital room.
“Then when he’s better, he can make an appearance in court,” Roper said, adding that a judge would likely be present for the bedside procedure.