COLUMBUS, Ohio (WCMH) — Criminals are getting their hands dirty by stealing used cooking oil from restaurants across central Ohio.

Sumit Majumdar, the president of Buffalo Biodiesel, reached out to NBC4 Investigates to get the word out about the slimy crime that he said has cost his company millions of dollars.

“It’s ballooning. It’s wiping out a third of our business,” Majumdar said. “To put that into numbers: $10 million to $15 million a year.”

Buffalo Biodiesel provides thousands of restaurants across 12 states with containers to dispose of used cooking grease. The company then collects the grease and processes it to manufacture biofuels. But as fuel has become pricier over the past year, the grease has become a more valuable commodity.

Sometimes, company drivers will arrive to collect the grease, only to find the container has been emptied already. Majumdar said he’s dealt with grease thefts in mid-Atlantic states — such as New York, New Jersey, and Pennsylvania — for several years, but told NBC4 he’s noticed more Ohio incidents in recent months.

In October, he reported thefts at a restaurant in Newark, and another in Pataskala.

“They’ll aggregate that oil and sell it through a broker, so that way, it’s kind of washed. And it’ll go off to a refinery, and they’re making a lot of money,” Majumdar said.

Alex Behnen, commander of the property crimes unit at the Columbus Division of Police, said that while these thefts have been reported, he doesn’t believe they are on the rise — just that they go underreported.

“The used cooking oil is taken by the restaurant operator, put in a tank in the back of their building and then collected most times by a third party once a month,” Behnen said. “There could be quite a bit of time that they may not notice their grease is gone.”

Grease thefts can be difficult to investigate as well, he said.

“Obviously it’s a liquid. It doesn’t have a serial number,” he said. “Most of the smaller restaurants that we do hear are having issues with this, they generally don’t have a security camera or really good lighting on those tanks where they place that grease.”

Behnen said legitimate collectors of used cooking oil typically arrive during regular business hours in large tanker-type trucks, with drivers in uniforms.

“Almost certainly if it’s after hours, small vehicle, panel vans,” Behnen said, “It almost certainly is not legitimate and they should call the police.”