The lone surviving suspect of the Boston Marathon bombings is awake and responding to questions from law enforcement officials, according to media reports.

Dzhokhar Tsarnaev, who is in serious condition as he recovers from wounds incurred in a firefight with police, including a bullet wound to the throat, is unable to speak, but has responded in writing, according to law enforcement sources.

Tsarnaev, age 19, and his brother Tamerlan Tsarnaev, who was killed in a shootout on Friday, are suspected of the bombings last week that killed three and left dozens injured. Dzhokhar Tsarnaev was captured late Friday after leading authorities on a 19-hour manhunt, which shut down much of the greater Boston region.

A law enforcement official confirmed to NBC News that Tsarnaev was conscious on Sunday evening, but declined to reveal what agents had asked him or share his responses. Authorities told NBC that Tsarnaev would be questioned without initially reading him his Miranda rights, citing a public safety exception.

Earlier Sunday, officials had expressed doubts if he would ever be able to recover enough to communicate with investigators.

Tsarnaev has yet to be charged as officials continue to investigate the bomb blasts. Prosecutors and law enforcement are hoping to understand the motive behind the attack and determine if others are involved or if the brothers planned further attacks. The suspect could face both federal and state charges.

His arrest has also sparked a renewed legal debate over the rights of suspects accused of terrorism.

The move to delay Mirandizing him led to criticism from the American Civil Liberties Union (ACLU), which has called on Tsarnaev, a naturalized American citizen of Chechen ethnicity, to be treated as any other suspect.

Many Republican lawmakers are urging that Tsarnaev be designated as an “enemy combatant,” which would allow authorities to deny him counsel and other protections afforded under the Constitution in order to seek more intelligence.

"We need to know about any possible future attacks which could take additional American lives," said Sens. John McCainJohn McCainDemocrats step up calls that Russian hack was act of war McCain: Trump admin must fill State Dept. jobs McCain says he hasn't met with Trump since inauguration MORE (R-Ariz.) and Lindsey GrahamLindsey GrahamGraham: 'I'm glad' Ivanka will be working in the White House Trump tweets promotion for Fox News show GOP senators pitch alternatives after House pulls ObamaCare repeal bill MORE (R-S.C.) in a statement last week. "The least of our worries is a criminal trial which will likely be held years from now."

But Senate Intelligence Committee Chairwoman Dianne FeinsteinDianne FeinsteinDems get it wrong: 'Originalism' is mainstream, even for liberal judges Human rights leaders warn against confirming Gorsuch Feinstein sees slipping support among California voters: poll MORE (D-Calif.) and other Democrats rejected calls to treat him as an enemy combatant as unconstitutional and said prosecutors and law enforcement could gather enough evidence without that designation.

“We don't need 'enemy combatant' to get all the information we need out of him,” said Sen. Charles SchumerCharles SchumerDem to Trump: 'You truly are an evil man' Dem senator: GOP controls all of gov't, so success or failure is on them Trump tweets: We’ll put together a great plan after Obamacare explodes MORE (D-N.Y.) on Sunday. "We don't have to cross the line and say he should be an enemy combatant, which could be challenged in court."

Tsarnaev could also face the death penalty if convicted on federal terrorism charges.

On Sunday, Feinstein said she believed there was sufficient evidence against the suspect to “likely be a death penalty case under federal law.”