BELLINGHAM, Washington (CNN) -- U.S. and Canadian authorities said Thursday they had arrested more than 40 people and broken up six rings that smuggled drugs across the border using planes and helicopters.

The cross-border drug runs got public attention in July 2005, when Playboy magazine profiled the practice.

Investigators have also seized 8,000 pounds of marijuana, 800 pounds of cocaine, more than $1.5 million in currency and two aircraft.

Marijuana was shipped south of the border while cocaine was smuggled north, said Peter Ostrovsky, who headed the investigation for U.S. Immigration and Customs Enforcement (ICE).

Investigators compiled evidence using video cameras hidden in national forests that caught helicopters, their skids laden with large bags investigators said contained drugs, landing in small clearings. (Watch the low-flying copter dropping dope -- 3:00)

The bags were loaded into waiting pickups and SUVs, with the transfer process taking as little as 43 seconds, investigators said.

In other instances, bags of marijuana were dropped from planes, or released from slings underneath helicopters.

The drug flights would fly low through the valleys of the Okanogan National Forests and North Cascades National Park, hidden from radar. (Map) Aircraft tail numbers were altered or concealed to avoid easy identification, smuggling aircraft were parked on farms instead of airports and unlicensed pilots did the flying, officials said.

Federal prosecutors in Seattle and Spokane, Washington, have issued 45 indictments and have arrested more than 40 people, an ICE spokeswoman said. The Royal Canadian Mounted Police made six arrests in Canada, she said.

Smugglers quoted in the Playboy article said authorities would never be able to stop their operations, but the U.S.-Canadian investigation, dubbed "Operation Frozen Timber," had begun more than six months earlier, after the Canadian police came across smugglers using helicopters.

Investigators say they are confident that they have arrested at least one of the smugglers quoted in the Playboy article, a pilot who was identified as "George."

Despite the arrests, investigators this week conceded that they have not stopped the practice and are unlikely to ever do so.

"I think we've shut down the half-dozen groups we've been working, but I can tell you this, there's a lot more out there," Ostrovsky said.

One reason the smuggling rings proliferate is the lucrative nature of their contraband.

Investigators said the marijuana being smuggled in from British Columbia is a potent "gourmet pot" known as B.C. Bud. It wholesales for $3,000 a pound in California, compared to $400-a-pound marijuana smuggled in from Mexico.

The investigation is continuing, authorities said.