By Nicole Chavez and Jason Morris, CNN

(CNN) -- One of the roommates of the man who carried out a series of deadly explosions in Austin, Texas, is still being questioned as part of the ongoing investigation, a Texas congressman said.

Texas Rep. Michael McCaul said authorities want to know whether Mark Anthony Conditt's roommate had any knowledge or involvement in the explosives that Conditt made.

The roommate was not identified.

Conditt, 23, is responsible of making seven devices, killing two people and wounding several others in Austin and near San Antonio over nearly three weeks. He blew himself up with a final bomb as police approached him last week.

Two of Conditt's roommates had been detained and questioned following his death last week. One of them was released within hours, but the other was not free to go until the next afternoon, police said.

They were not arrested and were not publicly identified.

Interim Austin Police Chief Brian Manley had left open the possibility the roommates could face more questioning as the investigation continues.

Manley has declined to discuss details about the investigation, CNN affiliate KXAN reported.

"Any person with knowledge of such an horrific act would have a duty to report it to the authorities and if they failed to do so could be complicit in the conspiracy," McCaul said.

McCaul, who is the chairman of the House Homeland Security Committee said investigators are combing through Conditt's cell phone and electronic devices as they look for clues that could lead them to his motive.