NEW YORK (Reuters) - An American citizen who authorities say supported al Qaeda and assisted in preparing a 2009 car bomb attack on a U.S. military base in Afghanistan could face new charges that carry the death penalty, a U.S. prosecutor said Thursday.

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The announcement came as Muhanad Mahmoud Al Farekh, 30, pleaded not guilty in federal court in Brooklyn to charges that he played a role in helping prepare one of two explosive devices for use in the Jan. 19, 2009 attack.

Prosecutors said an accomplice detonated one device, while Al Farekh’s fingerprints were found on packing tape for the second device, which a second accomplice carried and did not detonate. The military base was not identified.

In court, Assistant U.S. Attorney Zainab Ahmad said prosecutors were considering bringing charges over the death of Afghan nationals in the attack based on evidence authorities had been gathering over the last few months.

Ahmad said prosecutors had also obtained a search warrant for Al Farekh’s DNA to see if it matches a sample recovered from the packing tape.

“We expect in a month or two we’ll know what we can prove,” she said.

Seth Maher, Al Farekh’s lawyer, said the announcement meant the Texas-born man could face “potential death-eligible counts.”

He urged U.S. District Judge Brian Cogan to limit prosecutors from continuing to expand the case, which was first announced in April 2015 after Al Farekh was flown to the United States from Pakistan, where he was detained.

“It seems to me seven years is more than enough time to consider if a death can be added to these charges,” Maher said.

The hearing came after prosecutors unveiled a revised nine-count indictment on Wednesday charging Al Farekh with conspiring to murder Americans, use a weapon of mass destruction, bomb a government facility and aid al Qaeda.

Prosecutors initially accused Al Farekh of conspiring to support al Qaeda by traveling with two fellow students from the University of Manitoba in Winnipeg, Canada to Pakistan with the intention of fighting against American forces.

The other university students Al Farekh traveled with in 2007 included Ferid Imam, who has also been indicted and whose whereabouts are unknown.

Prosecutors said Imam provided training at an al Qaeda camp in Pakistan in 2008 to Najibullah Zazi and two other men later convicted of plotting a bombing attack in the New York City subway system.