Updated

A Detroit man accused of amassing weapons and buying explosives from an undercover agent has been indicted by a federal grand jury.

Sebastian Gregerson was arrested about two weeks ago and held on a criminal complaint, which is a temporary charge. The indictment was filed Thursday.

The 29-year-old is charged with possessing an unregistered destructive device and receiving explosive materials without a permit. Prosecutors have described him as dangerous, but defense attorney David Tholen says he's simply a survivalist.

Gregerson is in jail without bond.

Agents said they found several CDs with the name of cleric Anwar Al-Awlaki at Gregerson's home.

Al-Awlaki was influential among militants living in the West. His internet sermons called for a war against the United States. He was killed in Yemen in 2011.