Nassau County officials announced a major bust involving catalytic converter thefts.

They say they seized $3.9 million in cash in the one-year investigation, which also involved Homeland Security and the Postal Service.

Nassau officials said search warrants were executed Tuesday at two Long Beach residences where two brothers in their 20s were living.

Christopher Lau of Homeland Security said the case began as an investigative lead received from their St. Paul, Minnesota, office. They were then able to track down the lead to Nassau County.

"Make no mistake - these are not simple thefts," said Nassau County District Attorney Anne Donnelly. "These are criminal organizations that are profiting on a large scale."

The thefts of catalytic converts are so lucrative because of the metals inside of them have skyrocketed in price.

Nassau County Police Commissioner Patrick Ryder says rhodium costs $12,000 an ounce, palladium is $1,800 an ounce and platinum goes for $1,000 an ounce.

Nassau County Executive Bruce Blakeman says thefts of catalytic converters have gone up by 300% in the last year.

Authorities say their investigation will continue.

Ryder warned scrap yard owners who have bought stolen catalytic converters that they can no longer turn a blind eye.

"Because the door's going to be knocking, and it's going to be Nassau County police," Ryder said.