The Labor Department is investigating allegations of a theft of money from the union that represents most Metro employees, the local union president said yesterday.

The union does not know the source or the details of the allegation, said James M. Thomas, president of Local 689 of the Amalgamated Transit Union, which represents more than 6,300 Metro bus drivers, train operators, maintenance workers and other employees.

The union learned of the investigation a week ago when it received a D.C. Superior Court subpoena asking for the local's financial records and audit reports, said the union's attorney, Isadore Gromfine.

"No individual officers of the union were named or accused of anything" in the subpoena, Gromfine said. "We will fully cooperate. We have absolutely nothing to hide."

The union's books are audited every six months by the firm of Matthews, Carter & Boyce, Thomas said.

The last audit, for the six months that ended Dec. 31, turned up no sign of theft, he said.

None of the union's officers has been interviewed as part of the investigation, Thomas said.

The local's members will be assessed $30 each to help defray the costs of cooperating with the investigation, Thomas said.

The Labor Department would not comment on the investigation, a spokesman said.

Metro officials said they knew nothing about the investigation. "We don't have any knowledge at all," said spokeswoman Marilyn Dicus.