Police are warning gym-goers to be extra vigilant as a worrying trend emerges in gyms across the state.

Groups of young thieves are sneaking into gyms and snatching car keys from unattended bags before stealing vehicles from carparks.

3AW Mornings was contacted by one victim, a woman who had her car stolen while she was working out at Anytime Fitness in Point Cook last week.

Today, the Herald Sun reports up to five cars have been stolen from gyms in Werribee, Tarneit and Point Cook in the last week.

North West Metro Region Superintendent Therese Fitzgerald said the thieves often pose as gym-goers.

“People posing as gym users will follow somebody in behind, so tailgate them when they access the gym, or they might stand outside the gym and say ‘I’ve forgotten my access pass, can you let me in?’,” she told Neil Mitchell.

“They might pose as gym users by using the equipment. Often they’re wearing activewear.”

Ms Fitzgerald said the problem extends far beyond a a pocket in Melbourne’s west, and its not just one gang involved.

“Across the state, really, we’re seeing this across all regions,” she said.

“We’ve already arrested a number of young people, women and men from a range of different backgrounds.”

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Image: Kiyoshi Hijiki / Getty Images