PORTLAND — A Bath Iron Works employee has been charged with extortion after allegedly threatening to release documents about improper welding in Navy ships unless he was paid $5 million, federal authorities said Tuesday.

Harold L. Anderson, 37, of Waldoboro, was freed on his own recognizance after appearing before U.S. Magistrate David Cohen late Tuesday afternoon. The magistrate appointed lawyer David Pomeroy to represent Anderson, a BIW welding instructor who said he has just $21 in life savings after trying but failing to catch up with overdue bills.

“I’m winding up with nothing afterward,” said Anderson, who appeared in court wearing blue jeans and a black turtleneck sweater. Anderson, who declined comment on the extortion charge, faces up to 20 years in prison and a fine of $250,000 if convicted.

An affidavit from FBI Special Agent Gerald T. Mahoney says that on Thursday, a BIW official received a note demanding the $5 million payment.

On Monday evening, a caller who spoke to BIW Chairman William E. Haggett ordered that the money be taken to a location along state Route 209 in the nearby coastal town of Phippsburg, BIW spokesman Jim McGregor said. Police and the FBI were called in, and they arrested Anderson.

The FBI affidavit was placed under seal in U.S. District Court on Tuesday.

But U.S. Attorney Richard S. Cohen said in a statement that the affidavit describes “certain incriminating documents which were found on the defendant’s person at the time of his arrest.”

Pomeroy declined to discuss the case with reporters.

Some of Anderson’s family members were with him when he was arrested, but they were not involved in the incident and they were never taken into custody, Richard Cohen said.

Anderson said during his initial appearance on Tuesday that he lives with his wife and three children.

Cohen said the investigation was continuing. He did not know whether there would be any more arrests or any more charges.

A probable cause hearing was set for April 5.

McGregor said BIW received its initial contact when a corporate officer was phoned at home on Thursday night and told to look in his mailbox.

McGregor, who would not identify the corporate officer, said a package was found with shipyard documents inside, along with a “crudely written” note demanding $5 million. BIW officials then notified Bath police and the FBI.