SACRAMENTO, Calif. (AP) — Hundreds of federal and local law enforcement agents have seized roughly 100 Northern California houses purchased with money wired to the United States by a Chinese-based crime organization and used to grow massive amounts of marijuana illegally, authorities said Wednesday.

The raids culminate a monthslong investigation focusing on dozens of Chinese nationals who bought homes in seven counties. Most of the buyers were in the country legally and came from as far away as Georgia, Illinois New York, Ohio and Pennsylvania, U.S. Attorney McGregor Scott said.

Much of the pot was shipped back to those states through Atlanta, Chicago and New York City.

The drug is legal in California but requires permits to grow and can’t be sent across state lines. It is still banned by the U.S. government. Black-market pot farms are often set up in the inland region where authorities carried out the raids because it’s cheaper than the San Francisco Bay Area.

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“This criminal organization has put a tremendous amount of equity into these homes through these wire transfers coming in from China and elsewhere,” Scott said in an interview with The Associated Press. “We’re going to take it. We’re going to take the house. We’re going to take the equity.”

None of the buyers was arrested as authorities seized the houses in what the U.S. Department of Justice called one of the largest residential forfeiture operations ever. Prosecutors will now ask judges to transfer ownership to the U.S. government.

Authorities were trying to learn if the buyers were brought to the United States for the purpose of buying the houses and were indebted to the criminal organization. They are not ruling out criminal charges but have filed none at this stage of the investigation.

Down payments were financed by money wired from Fujian Province in China, authorities said. Many of the transfers stayed just below the $50,000 limit imposed by the Chinese government.

FBI Special Agent in Charge Sean Ragan, right, flanked by McGregor Scott, the United States Attorney For the Eastern District of California, discusses the months-long investigation that led to the law enforcement raids on illegal pot grows in roughly 100 Northern California homes, during a news conference, Wednesday, April 4, 2018, in Sacramento. (AP Photo/Rich Pedroncelli)

The buyers generally used the same Sacramento real estate agents, borrowed from private lenders who usually charge higher interest rates and require larger down payments than traditional banks, and used straw buyers who purchased the properties on behalf of the real owners.

A message left with the Chinese consulate general’s office in San Francisco was not immediately returned.

The federal crackdown on the illegal pot operations comes as California is months into creating the world’s largest legal marijuana market amid uncertainty about whether the U.S. government will try to shut it down.

More than 500 officers, including SWAT teams, fanned out over two days to search and seize about 75 houses and two real estate businesses. The remaining 25 houses were raided previously.

They seized more than 36,000 marijuana plants, 115 kilograms (253 pounds) of processed marijuana, at least $68,500 in cash and 15 firearms, including one that had been stolen. They also seized generators, one of which was strong enough to power three normal homes.

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Most of the suburban houses were valued at $300,000 to $500,000, though some were in rural areas and some in more upscale neighborhoods.

Black-market pot operations have been a widespread problem in Northern California for at least a dozen years. Sacramento officials have estimated that there might be as many as 1,000 illegal grow houses in California’s capital city.

Suburban tract homes are transformed with high intensity lights and irrigation pipes, gutted to add ventilation pipes and air filtration systems to vent the tell-tale smell through the attic, and stacked with tables full of marijuana plants that could produce multiple crops each year.

“It’s like industrial agriculture,” Scott said.

Authorities often are alerted when the houses catch fire because of illegal electrical hookups or when they are found to be using extraordinary amounts of electricity to power the equipment.

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