Police in Renton are warning residents about an increase in car thefts throughout the city over the past month.

A review of police reports shows a total of at least 12 stolen in just the past week.

“Above and beyond the monetary aspects, a car is often one of the biggest role players in people’s lives, and loss of a car can make it tougher to get to work, to get kids to daycare, and just to do everyday living,” Det. Robert Onishi said in an email.

According to Onishi, the most common cars stolen in Renton are Honda Accords, Toyota Camrys and Nissan Sentras that were built in the 1990s, though he said any car or truck is a potential theft to a skilled thief.

“They’re not stolen for their intrinsic value, they’re stolen because they are a means of transportation that many criminals lack,” he said. “Don’t make it any easier for these folks.”

Onishi, who has been working the car- theft beat since 2000, said January was the worst month for car thefts since he has been working. Whereas the previous high was 76 cars stolen in October 2008, in January there were 106 cars stolen in Renton. Onishi said some of the increase could be due to increases in population since then, but it still comes out to three-to-five thefts per day.

“Things kind of went completely off the charts,” he said.

Onishi said residents should take precautions to make themselves and their vehicles less vulnerable to thieves.

According to the detective, cars left running to warm up are especially vulnerable this time of year. Onishi said thieves look for “steamers,” or a vehicle whose exhaust can be seen while it’s idling, as easy prey.

He also warned of leaving cars unattended for any reason while running, not just to warm up.

“If they can take it, they will unless you make it tougher to steal,” Onishi said.

Another common scheme is for thieves to take advantage of people who leave a spare key in their car. Onishi said people who leave an extra set of keys in the center console or glove box can become double victims if a thief rummaging through the car finds the keys because now the other car or home is easily accessible.

“All of these crimes are quick, and we need the public’s help in catching auto thieves in the act,” Onishi said. “If you see someone trying car door handles, looking into parked cars, or otherwise acting suspiciously, it’s important to let know as quickly as possible.”