The thefts occurred late Friday night and into early Saturday morning in frigid temperatures, police said.
The thieves "gained entry" into unlocked cars and took cash and valuables that had been left in the vehicles, police said.
"Vehicle thefts have also occurred from residents who leave their keys in their vehicles or who start their car and leave it unattended to warm up," police said.
"The Trumbull police would like to remind all residents to always lock their vehicles and never leave valuables inside."
Anyone with information about the incidents is asked to contact the Trumbull Police Department at 203-261-3665 or via the anonymous and confidential tip line online at Trumbull-ct.Gov/policetips.
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