SACRAMENTO, Calif. — Police are arresting large numbers of Chinese nationals in raids on illegal marijuana operations in California, Colorado and other states, raising questions about who is financing these grow houses and recruiting the immigrants to tend them.

In one recent indictment obtained by McClatchy, money from a southern China bank account was transferred to California to pay for down payments on homes that later become grow houses, suggesting that some investors in China are putting money into the illicit U.S. marijuana market.

“These are sophisticated operations,” said Thomas Yu, a longtime Asian gang investigator with the Los Angeles County Sheriff’s Department. “When we hear about Asian gangs, we think about young guys doing drive-by shootings. This isn’t like that. These are organized ad hoc enterprises, run by businessmen. They are in it for the profit.”

In and around Sacramento, police have arrested numerous Chinese suspects in recent raids on indoor pot farms. But raids have also taken place in more far-flung locations, such as Garfield County in Colorado’s northwest corner.

Last year, Garfield Sheriff Lou Vallario and his deputies descended on an illegal marijuana farm, arresting 14 suspects. To Vallario’s surprise, all 14 were Chinese nationals.

Vallario and other law enforcement officials are quick to note that people from many backgrounds — U.S. citizens, Mexicans, Russians — are involved in the illegal marijuana trade.

“We’ve had nationals from all over coming to this part of Colorado,” he said. “There are grow houses popping up in every neighborhood.”

But in recent years, Chinese operators seem to be expanding their reach:

In three separate raids in September, authorities in California’s Yolo County and the cities of Roseville and Elk Grove arrested 13 Chinese immigrants in raids on marijuana grow houses.

In a case filed in U.S. District Court in July, prosecutors allege that 10 Chinese suspects with out-of-state driver’s licenses were growing marijuana inside nine Sacramento-area homes. More than 7,700 plants were seized.

North of Sacramento, Yuba County sheriffs arrested 14 Chinese — some U.S. citizens and some with Chinese passports — in three marijuana busts between March and May. Those raids hauled in 8,000 plants, six firearms and thousands of dollars in U.S. currency, according to the county, which says it has turned the case over to the U.S. Attorney’s Office.

In July, a federal jury in Nevada convicted a 66-year-old Chinese man, Jianguo Han, on charges of running a large-scale marijuana operation in two Las Vegas houses. A month earlier, Colorado indicted five Chinese immigrants and 69 other defendants. They are accused of participating in what Colorado Attorney General Cynthia Coffman called “the largest illegal marijuana trafficking ring” since the state legalized the drug in 2015.

Coffman and other law enforcement officials say that marijuana growers and smugglers are targeting states such as Colorado and California assuming they can operate in the shadows of commercial enterprises that are licensed to grow pot. Coffman called the June indictment “a prime example that the black market for marijuana has not gone away since recreational marijuana was legalized in our state.”

Yu, who has investigated scores of large-scale marijuana operations, say the Chinese grow houses share much in common. Many are purchased with cash and are located in quiet, unassuming suburbs. Electricians are brought in to bypass the electricity meters, so growers can tap a free source of power to run grow lights and fans.

They can reap enormous profits. A single pot house can produce three crops annually, which can net a grower $1 million or more, depending on the size of the grow and the quality of the bud, Yu said. Often the marijuana is shipped to markets on the East Coast, one reason that Chinese immigrants from New York have recently been arrested in Sacramento-area raids.

Yu said that he’s seen a general pattern with the pot-house caretakers he’s arrested. Many are experienced farmers from poor Chinese provinces, often in their 50s and 60s. Some have been smuggled into the United States, but many arrive with Chinese passports, presumably arranged by the grow house operators, he said.

Having obtained B-1 or B-2 visas, they are allowed to stay in the United States up to six months. If arrested, they often provide little help to investigators, even when Mandarin translators are brought in.

In Garfield County, Vallario and his deputies dug up 3,000 marijuana plants from the Chinese grow operation they raided last year. But when investigators tried to question the 14 Chinese suspects they arrested, they quickly encountered language barriers. “We didn’t do a very thorough job of interrogating them,” said the sheriff. He later turned the case over to the federal Drug Enforcement Administration, which declined to comment.

In Sacramento, attorney John B. Renwick has carved out a practice representing Chinese arrested on drug charges and other offenses. Fluent in Mandarin, with a bilingual website, Renwick said he’s represented 100 Chinese arrested for marijuana growing over the last decade. Often the court appoints him because of his language skills.

Like Yu, Renwick said many the Chinese arrested are recent arrivals, often misled into thinking that large-scale marijuana grow houses are legal under California medical marijuana law.

Yu said that China is a source for at least some the money financing grow houses, and the July indictment of 10 Chinese suspects supports his contention. Prosecutors in that case allege that one female suspect, Xiu Ping Li, received three separate wire transfers of $48,985 each in early 2016 to purchase three homes that ultimately became Sacramento grow houses.

The money was allegedly transferred from a China Construction Bank account in Fujian province to Li’s Bank of America account. According to the indictment, she is accused of international money laundering and other offenses. The money laundering charge could get her up to 20 years in prison.

In California and other states, Chinese busted in marijuana grow operations generally receive probation and face potential deportation. But for many years, China has generally refused to take back its citizens convicted of U.S. crimes, in part because the United States — out of human rights concerns — has refused to extradite Chinese that Beijing claims are criminal fugitives.

As a result, many Chinese busted for pot growing “end up in a legal limbo,” according to a California court interpreter involved in several of these proceedings.

“I’m aware of several cases where (Chinese) people have been waiting for months and months,” said the interpreter, who asked to remain nameless because he was not authorized to talk to the media. “China will not take them back. So they periodically report to an ICE agent in town and get on with their lives. But they have no legal status. Some are stateless. Their Chinese passports have expired.”

With the help of the interpreter, McClatchy contacted three Chinese currently on probation for involvement in a Elk Grove pot house that police raided last year. All three — Jiabin Haung, Jun Song Chen and Annie Hong — declined to be interviewed.