A man accused of phoning in a bomb threat to the Ann Arbor Transportation Authority on Friday morning is being held at the Washtenaw County Jail, jail officials said this morning.

Robert Allen Braun, 38, of Ypsilanti, was arraigned Saturday at the jail on a charge of filing a false report or threat of a bomb. He was arrested Friday night, not far from the AATA's Blake Transit Center in downtown Ann Arbor.

According to Ann Arbor police Det. Sgt. Brian Jatczak, Braun used a cell phone to call the AATA at about 10:30 a.m. Friday and "made a general statement that there was a bomb on a bus."

As law enforcement officials investigated, they took extra precautions when someone spotted a black box unattended at 1 p.m. on South Fourth Avenue between Liberty and William streets, police said. The Michigan State Police Bomb Squad determined an hour later that the box was not a threat, but a promotional item for the movie "Thor," currently in theaters. The box had no link to Braun, police said.

Investigators ultimately traced Friday morning's bomb threat to Braun's cell phone and found him sitting on a bench near South 4th Avenue and William Street at 5 p.m. Friday, Jatczak said. Officers arrested him and seized his phone.

Jatczak said he does not know why Braun would make such a threat.

During Saturday's arraignment, Braun said he has been seeing a psychiatrist and depends on Social Security disability benefits. He said he doesn't use alcohol or drugs and hasn't been convicted of a felony since 1995. Braun did not elaborate on his criminal record.

Washtenaw County court records show Braun does not have any convictions in the county, where he moved in May 2009, having previously lived in Detroit. If convicted of the felony charge, Braun faces up to four years in prison.

A preliminary hearing is scheduled for May 25.

Lee Higgins covers crime and courts for AnnArbor.com. He can be reached by phone at (734) 623-2527 and email at leehiggins@annarbor.com.