A lawyer for a Burnsville man accused of threatening to blow up an Amtrak train in Montana pledged a vigorous defense for his client.

Matthew McKittrick, one of two defense attorneys, said on Thursday that he and a colleague will soon "look very closely at all the details" behind the charges and "compare that to what [the prosecution] must prove. The defense will definitely put the state to its task."

Hussein Hassan, 24, was arrested Monday night in northwestern Montana, where the westbound Empire Builder was halted. He is accused of being drunk and unruly on the train.

Hassan later suggested in an empty threat to a sheriff's deputy that he left a bomb on the train, according to the charges. That prompted the evacuation of 140 or so passengers in blizzard-like conditions and delayed its trek to Washington and Oregon by 11 hours.

Hassan remains in the Glacier County jail in lieu of $100,000 bail. He has a hearing scheduled for March 9 on charges of felony criminal endangerment and misdemeanor disorderly conduct. He pleaded not guilty.

While being escorted off the train Monday night, Hassan said he was on his way to his sister's graduation in Seattle.

The U.S. attorney's office in Montana said it cannot confirm nor deny that there is a federal investigation into the incident. The Glacier County Sheriff's Office said that federal authorities are preventing the jail from releasing Hassan's photo.