Police have responded to 21 thefts from vehicles in a week-long period.
Cars were targeted from last Monday to Sunday, including near Lawrence Street and Melrose Drive.
Cars on streets along Beechworth-Wodonga Road, between Pearce and Lawrence streets, were also targeted.
"The majority of the cars were unlocked," Acting Senior Sergeant Mick Maley said.
"It was mainly cash that was stolen.
"It's a crime of opportunity."
The cars were all parked in residential areas.
Offenders will often go from vehicle to vehicle checking door handles, and only target those left unlocked.
"People need to just lock their cars," the officer said.
"Don't leave anything valuable in them.
"If people have information, please contact Crime Stoppers."
Call 1800 333 000.
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