Miscommunication between agents in two FBI field offices may have contributed to the failure to detect Fort Hood shooter Nidal Malik Hasan's contacts with a radical cleric in Yemen, National Public Radio reports.

The FBI's Washington field office received a file on Hasan containing two of his emails with radical imam Anwar Al-Awlaki last February, NPR's Dina Temple-Raston said, citing sources familiar with the Hasan investigation. But there was no communication between the Washington office and the San Diego field office – which sent the original file – for three months.

By the time the two offices connected, an additional 16 emails between Awlaki and Hasan had been intercepted in San Diego. Those exchanges were not forwarded to Washington and the Washington agent didn't ask whether new intelligence had been collected.

Among those 16 emails was one in which Hasan mentioned Hasan Akbar, a Muslim soldier who killed two comrades and wounded 14 others when he threw a live grenade into a tent in Kuwait before the 2003 invasion of Iraq. According to Temple-Raston's report:

"In the e-mail to the imam, Hasan asked whether Akbar would have been considered a shaheed — or hero — for his actions. Given what happened later at Fort Hood, investigators say this e-mail now appears suggestive. But at the time it was not conclusive. Investigators in San Diego weren't alarmed by the query because it appeared to be consistent with research Hasan was doing at Walter Reed. The Akbar case was thought to be at the center of his research."

Since the Nov. 5 Fort Hood shooting spree, which left 13 people dead, reports have surfaced showing that Hasan was chastised for proselytizing to his patients and created concern with a PowerPoint presentation given at Walter Reed Army Medical Center that seemed to justify violent jihad. Witnesses say he shouted "Allahu Akhbar" before opening fire.

Awlaki called Hasan a hero in the wake of the massacre. While living in the United States, he repeatedly was investigated by federal law enforcement but the only charges against him were withdrawn before he was taken into custody.

Since moving to Yemen in 2002, his sermons are considered influential among jihadists.