OAKLAND, Calif. >> A man suspected of making threats that a bomb would explode on a Southwest Airlines flight departing from the Oakland International Airport was free on bail today as authorities delved into his background.

Authorities arrested 32-year-old Arpan Shah, of Sykesville, Md., and took him to the Glenn Dyer Jail after Southwest Flight 5135 returned to the gate on Tuesday, Alameda County Sheriff’s Office spokesman Sgt. Ray Kelly said.

His father told WBAL-TV that his son had been drinking beer before the flight and that the incident was a misunderstanding.

The flight taxied from Gate 6 around 2:30 p.m. on its way to Baltimore when Shah started ranting that he would blow up the plane and that it was going to blow up, Kelly said. The plane’s pilot then returned to the gate.

“We don’t know why he was acting the way he was acting,” Kelly said. “We don’t know if there are mental issues going on there, or what it might be but we’re looking at everything.”

The FBI also was investigating, he said.

Passengers exited and went back through the security screening, and a bomb squad checked all departments of the plane and didn’t find anything, Kelly said.

The plane eventually left for Baltimore three hours after its scheduled departure, Oakland Airport spokeswoman Keonnis Taylor said.

The rest of the airport’s operations went on uninterrupted.

“This is the busiest travel time of the year. People are going to see family and friends all around the country,” Kelly said. “To yell something like that is like yelling, ‘Fire,’ in a crowded building.”

Several passengers filled out citizen arrest forms. Shah is expected to be charged with making criminal threats.