The surviving suspect in the Boston Marathon bombing, 19-year-old Dzhokhar Tsarnaev, has regained consciousness and is responding to questions in writing, according to USA Today.
Tsarnaev is in a Boston hospital and unable to speak because of a gunshot injury to the throat.
Authorities have suggested the bullet wound may have been self-inflicted by the suspect in order to avoid capture.
Earlier Sunday (local time), Boston Police Commissioner Ed Davis said that Tsarnaev was not in any condition to be interrogated.
Reports circulated Sunday that federal officials were considering formally charging the suspect at his heavily guarded bedside.
However, officials later said no charges would be filed on Sunday.
Meanwhile, lawyers with the American Civil Liberties Union (ACLU) protested in a statement Sunday against the decision by the US Department of Justice to waive the rights of Tsarnaev to remain silent in the face of questioning and to legal representation.
The so-called Miranda rights apply to every accused person in the United States. Following a previous attempted terrorist bombing in New York's Time Square, however, the US government created an exemption in cases of the immediate danger of terrorism.
Under that, Miranda rights could be set aside and suspects identified as "enemy combatants."
In a statement, ACLU executive director Anthony Romero said every suspect deserved the right to the Miranda rules and that the exception for public safety should be used only in the most limited circumstances.
The abrogation of these rights would impede the ability of the justice system to come to fair conclusions, he added.
Conservative politicians have expressed the opposite opinion, with Republican Senator Lindsey Graham stating on Saturday that the last thing the country needed was for the Boston terrorist suspect to remain silent.
His conservative colleague and former presidential candidate John McCain also called for the suspect to be treated as an "enemy combatant."
After his capture on Friday, Tsarnaev lay in the same hospital as 11 of the victims of the twin blasts of April 15. Tamerlan Tsarnaev, his 26-year-old brother and alleged co-conspirator in the attacks, died after a firefight with police earlier that day.
The Boston Globe reported on Sunday that after Monday's bombing Dzhokhar Tsarnaev returned to the University of Massachusetts Dartmouth, where he was enrolled, on Wednesday. He worked out in the gym and even attended a party.
"He was just relaxed," said a fellow student.
Interfax news agency cited anonymous sources as saying that Russian authorities had no evidence of a connection between the two brothers and the conflict in the northern Caucasus, though the two men were of Chechen origin. Russian security forces would, however, continue to pursue possible leads in the matter, the report said.
US media earlier reported that investigators in Boston were looking into links between the Tsarnaevs and a group of terrorists in Chechnya. Tamerlan is said to have spent several months Chechnya and neighbouring Dagestan in 2012.
According to Russian media, Anzor Tsarnaev - the father of the two suspects - has expressed the wish to bury his son Tamerlan in Degastan, where the father currently resides.