The keys were left inside three vehicles reported stolen earlier this month in the Lincoln Park and Park West neighborhoods on the North Side.
In each of the thefts, the keys to the vehicle were left inside at the time they were stolen, Chicago Police said.
The most recent theft happened about 5:40 p.m. March 9 in the 500 block of West Deming, police said. Earlier thefts happened about 4 p.m. March 5 and between 6:30 and 9 p.m. March 2 in the 2400 block of North Lincoln.
Anyone with information should contact Area North detectives at (312) 744-2070.
