Portland has identified a culprit in the city’s sharp increase in car thefts last year.

Complacency.

Operators of most of the stolen cars had left the keys in them or left them running, police say. Most were recovered within days, not far from where they’d been taken.

“More often than not, we find them after they’ve been issued parking tickets or towed,” said Lt. Gary Rogers, head of detectives for the Portland police.

The number of cars stolen in Portland jumped from 58 in 2010 to 91 in 2011, a 63 percent increase.

Nationally, car thefts have gone down each year since 2003. They declined by 5 percent in the first half of 2011 compared with the same period in 2010, according to data from the Insurance Information Institute.

Portland reports car thefts to the state and the FBI, but most are not legally classified by police as motor vehicle theft, a felony. When stolen vehicles are recovered, the charge — when an arrest is made — is unauthorized use of a motor vehicle, a misdemeanor.

Portland police made arrests in about 27 percent of the 91 stolen car cases last year — the national average was 12 percent.

Although car thefts jumped last year in Portland, there are fewer thefts here than in comparably sized cities, according to Michael Barry, spokesman for the Insurance Information Institute.

Maine historically has a low rate of car theft per capita, with 76 cars stolen per 100,000 in population in 2010. The national average was 239 and one of the worst areas of the country for stolen vehicles, California, had 413 vehicles stolen per 100,000 people.

Portland, with a population of a little more than 64,000, had a rate of 141 cars stolen per 100,000 residents last year.

Most Portland car thefts fall into one of three categories:

• The car is loaned to somebody who does not return it.

• The car is taken — typically from a convenience store, gas station or fast food restaurant — when someone leaves it running.

• A car burglar finds the keys in the ignition, or in the glove box, ashtray or the compartment between the seats.

“When motor vehicle burglars are going through cars looking for iPods and GPSs, when they stumble across a set of keys, they use the car to transport the booty across town,” said Det. Barry Cushman, who investigates many of the city’s car thefts.

Cushman said only a handful of the cars stolen in 2011 have not been recovered.

Cushman could recall only one case where a car was broken into and the ignition forced. In that case, police believe the thieves were stealing a spool of copper wire and needed a vehicle large enough to hold it. They forced the van’s ignition and removed the seats.

The van was recovered in Windham a few days later.

Barry of the insurance institute said the increase in stolen vehicles in Portland probably won’t result in higher insurance premiums because rates are based on claims. If cars are recovered intact, the owners don’t need to file claims, so rates aren’t affected, he said.

In parts of the country where car theft is a major problem, the cars often end up in “chop shops,” where they are stripped and the parts sold on the black market, Barry said.

Barry said that leaving a vehicle running while going into a store is unheard of in New York City, where the institute is based.

“The idea of seeing a vehicle idling with no one in it, I think people would probably report it as a suspicious vehicle rather than get in it,” Barry said. “I think the reaction in Manhattan would be to run away rather than run toward it.”

For victims, car theft can be costly and inconvenient — even if the car is found.

Sara Deane, manager of Standard Baking Co. on Commercial Street, said the shop was broken into Christmas Day. The thief stole the bakery’s van and used it to cart away other loot.

The bakery had to rent a van to make its early morning deliveries until the stolen vehicle was found a week later, just a few blocks away.

The bakery had to pay for the rental, a tow, a jump-start and to hire a mechanic to examine the van for damage — a new engine had been installed the day before it was stolen.

But the money wasn’t the chief concern.

“It’s more of a pain in the neck,” Deane said.

Staff Writer David Hench can be contacted at 791-6327 or at:

dhench@pressherald.com