Dzhokhar Tsarnaev.Dzhokhar Tsarnaev.

The surviving suspect in the Boston Marathon bombings remained in serious condition in the hospital yesterday, unable to speak due to injuries to his neck and tongue sustained while on the run from police, officials said.

The US Federal Bureau of Investigation still was unable to interview Dzhokhar Tsarnaev, 19, Boston Police Commissioner Ed Davis told CBS TV, and authorities may never be able to speak with him, Boston Mayor Thomas Menino said.

The suspect was in Beth Israel Deaconess Medical Centre while US Attorney Carmen Ortiz, the federal prosecutor for the Boston area, was working on filing criminal charges,.

Tsarnaev was shot in the throat and had tongue damage, said a source close to the investigation, speaking on condition of anonymity.

“We don’t know if we’ll ever be able to question the indi­vidual,” Menino told ABC’s This Week programme.

Investigators were seeking a motive for the Boston Marathon bombings and whether others were involved besides the ethnic Chechen brothers they suspect carried out the attacks.

The other identified suspect, older brother Tamerlan Tsarnaev, 26, was killed during a firefight with police on Friday, in the middle of the dramatic 26 hours between when the FBI released pictures of the two suspects and Dzhokhar Tsarnaev’s capture in the Boston suburbs.

Two bombs made in pressure cookers and packed with ball bearings and nails exploded at the Boston Marathon on Monday, killing three people and injuring 176 and setting of a tense week in the US that culminated in a massive manhunt on Friday with the greater Boston area on lockdown.

The two brothers may have been readying for a second attack at the time of the shootout, Davis told CBS. Early indications were the brothers acted alone.

When police were able to move in after the hail of bullets stopped, they found unexploded devices littering the street and one in the carjacked SUV that the brothers had been driving. The devices contained the same type of shrapnel used in the marathon bombs.

“There is no doubt that they were made by these two guys,” Davis said.

Police finally found the suspect cowering in a boat in a backyard in Watertown, hours after police went door to door searching for him after he escaped on foot.

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