OAKLAND (KRON) — A Tracy man has been convicted in a nationwide jewelry robbery ring involving Craigslist ads being used to lure victims, according to U.S. Attorney spokesman Abraham Simmons.

Michael Anthony Martin, 42, was convicted in U.S. District Court in Oakland on Thursday of conspiracy to commit robbery affecting interstate commerce and robbery affecting commerce, the U.S. Attorney’s Office said.

Jurors found that Martin robbed victims on four separate occasions and conspired to rob victims selling jewelry on Craigslist, according to prosecutors.

Martin faces a term of 20 years in federal prison when he’s sentenced by Judge Jeffrey White on April 19.

The U.S. Attorney’s Office said Martin was part of a seven-member robbery crew that targeted individuals selling high-end jewelry such as diamonds and Rolex watches on Craigslist.

The robbery crew targeted victims nationwide, including the Bay Area, and was responsible for numerous robberies and attempted robberies between November 2012 and December 2013, according to prosecutors.

Crew members frequently posed as music producers or pretended to be in the market for diamond engagement rings when they contacted their intended victims by e-mail or cell phone and negotiated a price to purchase the jewelry item, the U.S. Attorney’s Office said.

The conspirators then lured their victims to the Bay Area, sometimes by paying for the victim’s airplane ticket or promising to reimburse the victim for travel, according to prosecutors.

Robbery crew members often posed as airport limousine drivers and picked up victims at the airport using a rented SUV, prosecutors said.

Victims, believing they were going to meet the buyer at a jewelry store or bank to complete the sale, were instead delivered to a different predetermined location where two or more additional crew members robbed them, using guns and physical violence, according to prosecutors.

The U.S. Attorney’s Office estimates that the robbery crew stole more than $500,000 worth of jewelry from victims who traveled from more than six states, including California, Arizona, Colorado, Oregon, Washington, and Wisconsin.

A spokesman for the U.S. Attorney’s Office said he’s not sure of the status of the cases against the other alleged members of the robbery crew.