Keene police are investigating a string of thefts from four unlocked vehicles on the city’s east side.

The thefts occurred sometime between Sunday evening and early Monday evening, when they were reported to police, Lt. Steven Tenney said Tuesday.

Vehicle owners reported cash and loose change missing from their cars. The owners of two vehicles parked at 42 Elliot St. told police they thought they had locked their doors, but police found no damage to the cars, Tenney said. Both of those vehicles had items strewn about their interior, and a combined $70 in cash missing.

Two other vehicles — one at 49 Water St. and another at 13 Willow St. — had small amounts of change missing, Tenney said.

Police continue to investigate these incidents, but in the meantime Tenney said the best way to prevent this sort of theft is to lock your car doors.

“In this case, it looks like it was just change, so it’s not like anything was left out inviting,” Tenney said. “But clearly, any valuable personal belongings should not be left overnight in cars, and they should be locked at all times, even if you think it’s just for a few minutes.”

Car break-ins and thefts were reported earlier this month in Keene on Brook, Beech, Gurnsey and Roxbury streets.