Jersey Police has arrested four teenagers on suspicion of taking a vehicle without the owner's consent after a car was found crashed in St Ouen on Sunday morning.
Officers say they are boys aged 17 and 18, and girls aged 13 and 15.
They want to speak to anyone who may have information about a third male they believe to be involved.
Police are urging people to make sure they lock their cars and take their keys with them after a rise in related crimes.
"We're seeing increasing numbers of vehicle crime, including stolen vehicles, and thefts from parked cars," Det Ch Insp Mark Hafey said.
"Although we live on a very safe island, there are individuals who choose to commit crimes, let's not make it easy for them.
"Islanders must take precautions to prevent these criminals from stealing items and causing damage.
"We all have a responsibility to keep our possessions secure, and this includes our cars."