Metro Transit officials confirm that they are wrapping up a four-month investigation of employees at the Hiawatha light-rail maintenance facility in south Minneapolis.

A spokesman on Thursday told the Star Tribune that he was not able to give many details about the probe, which began in December and is likely to wrap up soon.

"We can't comment on the nature or the findings of the investigation at this point because it is not yet final," said Metro Transit spokesman John Siqveland. "Metro Transit takes this situation very seriously."

The agency did not say which employees or how many are under investigation. Metro Transit also did not disclose the reason for the investigation, which is being conducted by an outside agency.

According to a KSTP-TV report, the investigations includes managers and hourly employees and involves employees allegedly trading pills and firearms for coveted overtime shifts.

No disciplinary action has been taken at this juncture, Siqveland said.