The spike in oil prices since the Iran war began this year has attracted more thieves, and they are increasingly professional criminals.

West Texas Intermediate crude is up 60% so far this year, and fuel prices have risen even more as global refining capacity has fallen due to the Mideast and Russia-Ukraine wars.

While oil theft has long been a part of the industry, the problem has become prevalent enough for the Dallas Fed to ask about in its quarterly surveys.

The latest one showed that nearly half of firms that are primarily focused in the Permian Basin said their operations have been impacted by theft in oil fields. By contrast, 86% of firms operating mostly outside the Permian said they were not impacted.

The Permian is the heart of the oil patch and the epicenter of the shale revolution that has transformed the U.S. into an energy superpower.

It stretches across the vast expanses of West Texas and southeastern New Mexico—and is dotted with drilling rigs, pipelines, trucks and other infrastructure necessities.

That’s made the Permian a target-rich environment. And now that U.S. oil prices have been hovering around $100 a barrel lately, criminals can’t resist the payoff.

According to the Dallas Fed survey, 32% of executives who were impacted by oil theft said it had increased slightly over the last 12 months, while 47% said it remained the same, and 22% said it decreased slightly or significantly.

Nearly half of the oil executives (47%) said the most common form of theft was targeted and organized, while 42% described it as opportunistic petty theft.

Still, the losses were relatively minimal, with 84% saying the financial impact of the theft was low.

A year ago, the Dallas Fed asked a slightly different set of questions about theft, including what exactly was stolen: 61% said crude oil; 58% said piping, valves and wiring; 39% said equipment; 27% said tools; and 12% said construction equipment and vehicles.

Theft can also be committed by other firms. In August, executives from a wastewater disposal company were charged with felony oil theft, money laundering and organized crime.

It was part of an investigation dubbed Operation Black Market Basin that resulted in the seizure of more than $12 million in petroleum products, vehicles, cash and other assets, according to the Texas Railroad Commission, which regulates the industry.

The investigation involved petroleum allegedly acquired and sold across Texas, New Mexico and Oklahoma, the commission added.

And in April, federal prosecutors announced charges in a large-scale oil theft conspiracy in the Permian Basin to transport stolen crude oil across the New Mexico-Texas border for resale.

Howard County Sheriff Stan Parker told Texas Public Radio in May that his county, which is near the Midland-Odessa oil hub, sees “probably over 1,000, 1,500 barrels of oil reported stolen every month.”

“Our problem is we don’t know who’s supposed to be there and who’s not,” he added. “If I pulled up on a tank battery right now, I don’t know if you can be there or you’re not. I don’t know if you’re drawing water off of it. I don’t know if you’re pulling oil. It’s got very complicated.”

This story was originally featured on Fortune.com