Upscale California city where housing costs are double the national average is OVERRUN with indoor drug dens

Sandwiched between the San Joaquin River and a trio of stunning national parks, the California city of Antioch seems like a peaceful part of the state's East Bay region, but in reality, it harbors an enormous underground criminal enterprise.

You'd never know it based on the wealth of the neighborhood. In fact, residents fork out 93 percent more than the national average to live in the upscale area, with the median house costing $588,000, while renters pay a median $2,850 per month, according to Fly Homes .

But the Golden State city's sunny exterior belies the shady underground weed trade that operates behind the walls of hundreds of the city's cookie-cutter homes.

Antioch Police raided around 60 alleged illegal marijuana dens over the past two years, according to NBC - and officers believe there could be hundreds more in operation.

Despite the high number of busts, only two people have been arrested and charged - and both got away with misdemeanors, thanks to California's lax laws.

While the median household income in Antioch is $90,709, some residents are making a great deal more through the shady trade.

An April drugs bust at a fancy five-bedroom, two-story Antioch home uncovered hundreds of thousands of dollars worth of illegal cannabis in the one residence alone.

Officials revealed the property belonged to an Oakland police officer - Samson Liu, 38 - who has since been placed on administrative leave.

It's unclear whether Liu lived in the home or rented it out to tenants, and no arrests have yet been made.

In another raid this spring, authorities uncovered around $1 million worth of illegal marijuana in another five-bedroom home on the affluent Shell Ridge Way.

Bill Jones, chief of law enforcement at the California Department of Cannabis Control, told CNN the illicit weed operation in Antioch is largely run by 'the Chinese criminal syndicate'.

In fact, the operation is so extensive that law enforcement believes there are more Chinese nationals within the illegal marijuana trade than gang members from Mexican cartels.

However, Vanda Felbab-Brown, a Brookings Institute expert on international crime, told CNN that Chinese and Mexican criminal groups also often work together to traffic Chinese migrants into the US for work in the illegal weed trade.

She told CNN the US government urgently needs to increase its surveillance of the issue.

'We have been prioritizing China military decision-making, but Chinese organized crime and organized crime more broadly has not been a high priority in intelligence collection,' Felbab-Brown said.

'That needs to change.'

The underground marijuana trade in Antioch is just the tip of the iceberg representing a state-wide problem across California.

Golden State criminals found guilty of dealing any amount of illegal weed will only face misdemeanor charges, apart from in extreme cases.

Exceptions include if the illicit marijuana was sold to a child, or if the culprit was already a registered sex offender.

Siskiyou County Sheriff Jeremiah LaRue, whose northern California district is crawling with the illegal trade, told CNN : 'You can have seven plants or 70,000 plants and it still is that same misdemeanor violation.

'It's actually just a joke.'

In fact, the state is responsible for producing around 40 percent of the nation's weed, according to economist Beau Whitney, and 75 percent of this economy is illegal.

California legalized recreational marijuana in 2016, but sellers who skirt the rules, fees and taxes involved in operating within the highly-regulated legal trade have proliferated since.