D.C. police are investigating an unusual whodunit. This time, they're the suspects.

The caper began in the wee hours of Aug. 9 when police charged a homeless man with burglary for an after-hours picnic inside a cafe in the Chevy Chase neighborhood of the District. The man was flush with cash when arrested--$12,000, the source of which was apparently legitimate but not entirely clear. He was booked and processed, and his cash was placed in a department safe for, well, safekeeping.

By the time he returned to claim it this week at 2nd Police District headquarters, it had vanished.

A source familiar with the case said all 2nd District officers' lockers were searched on Wednesday. Only a few officers had access to the second-floor administrative safe where the cash was stored. It is generally used by lieutenants, captains and station Cmdr. Shannon Cockett, who is overseeing the investigation of her troops.

"They say the safe was ajar when they found [the money was missing], implying it possibly was left open," the police source said. "It really doesn't make a lot of sense. They changed the combination in July, so only a very few people had access to that safe."

The way police tell the story, just after midnight on Aug. 9, John Mihas was rattling doors on Connecticut Avenue, looking for a place to sleep. When he tried the basement door behind the Bread & Chocolate store in the 5500 block, officials said, the door swung open.

Officials said Mihas indulged in a brief bounty of wine and food, even helping himself to some employee uniforms before Officers Dalon Thomas and Walter Freeland arrived, responding to a burglar alarm.

As they peered into the store's windows, looking for signs of a break-in, Mihas popped up and peered back at them, officials said. Mihas surrendered.

The officers took Mihas's money back to the 2nd District station. They gave it to Capt. Marcus Westover, who logged in the cash and put it in the safe, sources said. Sometime later, it vanished.

"We are taking this matter extremely seriously," Police Chief Charles H. Ramsey said in a statement released through a spokesman. "We did launch an investigation as soon as it came to our attention."

Officers nicknamed Mihas "Elvis" because of his slicked-back black hair. He was known to them for another reason: He once was found carrying $35,000 in cash and $17,000 in food stamps, the source said.

Police said he is one of a small band of homeless men who frequent the alleys, parks and benches around Chevy Chase Circle. They sometimes get $20 at a time from well-heeled strangers--but not enough to amass that type of bankroll.

Officers couldn't explain why Mihas had so much money, but they didn't suspect it was ill-gotten and let him go on his way, the source said. One officer said he heard rumors that Mihas earned money from a veterans' pension.

Mihas did not respond to an interview request taped to his shopping cart, parked a few doors away from Bread & Chocolate.

The D.C. police department has investigated numerous thefts of firearms, drugs and money from its property rooms in the past, but few such thefts have been reported in recent years.

The D.C. Court of Appeals ruled in April that the District was not liable for a Kentucky woman's $3,709 that was stolen from the 2nd District property room after she was arrested and sent to St. Elizabeths Hospital in 1993. Attorneys for the District argued that taxpayers should not be liable for employees' crimes.

Officer Mark E. Mehlman, who officials said set fire to the property room to conceal that crime, drove to the Shenandoah National Forest and killed himself with his police-issued pistol.

An American Civil Liberties Union lawyer argued that police failed to establish adequate controls or conduct audits. Department rules require that large sums of cash be transferred to a central vault.

Staff writer Phuong Ly contributed to this report.