EVERETT — Big rigs worth big bucks often leave few clues when they’re stolen.

That’s the challenge the Snohomish County Auto Theft Task Force is facing these days.

In recent months, nine pieces of heavy equipment belonging to Snohomish County companies have been reported stolen. All told, they’re worth about $275,000.

In the last week of December, three of those machines were recovered in Pierce County.

Heavy equipment doesn’t require a title transfer, as other vehicles typically do.

In the past, heavy equipment thefts have occurred most often in good weather months, but that hasn’t held true this winter. “It really hasn’t slowed down much since summer,” said Terry Haldeman, a detective with the county’s Auto Theft Task Force, which works closely with other law enforcement agencies across the Puget Sound region.

“Construction is very active,” he said. “We’re having a very mild winter and construction has continued on.”

During a three-month period over the summer, there were 89 reports of heavy equipment being stolen across Washington and Oregon. Typically, the value of stolen heavy equipment across the country reaches $400 million each year. Loaders and tractors are particularly popular with thieves.

One excavator, belonging to a Monroe contractor, has been stolen twice during the past two years. More than a year ago, it was taken from a Bellingham construction site and recovered near Clearview.

A week ago, it was stolen again, this time from a Pierce County job site. Detectives there found it Monday on private property in Roy. It was being used to bury a Dodge Durango, Haldeman said. Detectives were investigating whether the Durango was stolen, too.

On Wednesday, law officers recovered another excavator and walk-behind loader belonging to a Marysville company. A farmer from Buckley had purchased both pieces of equipment after taking out a Craigslist ad but became suspicious after he was able to buy them at such a reduced rate, Haldeman said.

“He was unsuspectingly purchasing stolen equipment,” Haldeman said.

Several pieces of equipment have not yet been found.

In August, for instance, a 2014 John Deere mini-excavator disappeared from a locked job site near Lynnwood. Thieves cut a lock and backed the excavator out and onto a trailer before closing the gate, officials said.

In September, a Caterpillar 236D skid-steer loader was taken from an Edmonds construction site.

In December in Lake Stevens, someone stole a mini-excavator from a land owner’s property and a Kubota B21 tractor from a construction site.

Last week, someone stole a John Deere crossover utility vehicle from a Snohomish business.

“A lot of it is being bought and sold for drugs,” Haldeman said. “The crime doesn’t take a holiday.”

Roughly 20 percent of stolen heavy equipment is recovered, according the National Insurance Crime Bureau and the National Equipment Register. That sticks insurance companies, rental businesses and equipment owners with the bill.

In 2013, the Snohomish County Auto Theft Task Force recovered more than $500,000 in stolen heavy equipment.

Often, the sales occur quickly, at pennies on the dollar, Haldeman said.

Eric Stevick: 425-339-3446; stevick@heraldnet.com.