A New York Diamond District jeweler staged two gem heists and was plotting a third robbery when he was arrested Dec. 5, Manhattan federal prosecutors reportedly said.

Brian Greenwald, 37, and 11 others were charged in the bungled robbery of $1 million in jewels from a FedEx truck on Dec. 20, 2007, the New York Daily News reports. The thieves were forced to abandon their bounty on a Brooklyn street when hijackers couldn’t figure out how to detach six cargo containers from the floor of an 18-wheeler they stole from its driver at gunpoint.

Greenwald also is suspected of enlisting a pair of armed bandits dressed as FedEx workers to rob his business at 580 Fifth Ave. off W. 47th St., of nearly $5 million in valuables in 2005 so he could collect the insurance, the newspaper reports. In the heist, thieves busted into the store and bound five employees with plastic handcuffs before running off with loose jewels tossed into duffel bags, the newspaper reports.

The New York Post identifies his business as Doppelt & Greenwald.

Greenwald hasn’t been charged with that crime, but his involvement is included in an FBI affidavit filed in Manhattan Federal Court, the newspaper reports.

City cops became suspicious of Greenwald in the 2005 robbery because he showed little emotion for someone who had just lost a small fortune, the newspaper reports.

Greenwald was being held in a Brooklyn federal jail as of Monday following his arrest, the newspaper reports.

JCK