HOUSTON -- Two armed men stole $1 million worth of jewels from a man outside of a gas station, police told KPRC Local 2.

Houston police said a jewelry dealer from New York was robbed after he pulled into a Chevron Station on Bissonnet Street near Kirby Drive on Wednesday.

The dealer told investigators that he believed three men followed him to the gas station.

They covered their faces with bandanas and slashed his tires to escape.

This is the third armed robbery of a jewelry dealer in recent weeks.

Another dealer reported being beaten and robbed in the parking lot of a Holiday Inn Express in Montgomery County on April 28.

He told Montgomery County sheriff's deputies that three or four men who covered their faces attacked him. Investigators said about $600,000 worth of jewelry was taken in that robbery.

A third dealer said he was robbed on May 1 in the Rice Village area.

Local jewelers said some of the thieves are believed to be from a Colombian mafia group.

"They'll come and do a rash of robberies and then they'll move on. Then, they will hit another city and do the same thing," jeweler Ronnie Bullock said.

Some local jewelers admitted that their sales reps sometimes do not carry inventory anymore for protection. Instead, they carry lists and catalogs of merchandise.

They said the loss affects the jewelry industry and sometimes closes businesses down.

"Unfortunately, most of the robberies -- they don't recover the jewelry. They may catch the guys, but they don't recover the jewelry," Bullock said.

Police do not have a good description of the suspects. They said they are looking for a silver Mitsubishi Galant and a white Chevrolet SUV that were seen at the other robberies.

Anyone who spots suspicious people walking around or watching jewelry stores is asked to call the Houston Police Department.