Lincoln police on Tuesday warned automobile owners to lock their vehicles and take their keys inside after a series of car thefts in the first two weeks of September.
Between Sept. 1 and Sept. 12, 28 vehicles were stolen in Lincoln, Officer Angela Sands said.
That's a jump from 18 in the same time period last year but on par with the 27 stolen in the period in 2015, Sands said.
Overall, 256 vehicles have been stolen this year.
At least 11 of the cars were unlocked, and some had keys inside, Sands said.
The number of cars left unlocked has police alarmed, she said.
"These are crimes of opportunity," Sands said. "People often move on to the next car if they try your door handle and it's locked."
Only 15 of the stolen vehicles have been recovered. Most of the thefts are still being investigated.
Police have blamed two teenagers for stealing some of the cars during a spree in the city and elsewhere in Lancaster County. Those teens were arrested after a pursuit Sept. 5, in which police used a spike strip to bring the chase to an end.