RIDGEWOOD - Police in several northern New Jersey towns are warning residents not to leave valuables in plain sight in their cars while they work out at their local gym.

Investigators say the robberies happen during the day when victims leave handbags and other valuables where they can be seen, making them an easy target for thieves.

Gym-goers in Ridgewood say they hadn't considered the issue before now. In the last several months, thieves have stolen from locked cars while the owners were inside working out.

"I park, lock my door, and go in," says Antoinette Martorano, of Ridgewood. "And I do leave my pocketbook in the car, which I shouldn't." She says in a town she considers safe, it wasn't something she had thought about.

Police say it's happening in broad daylight. In the last several months, the thieves have hit health club parking lots in Paramus, Ramsey, Mahwah, Ridgewood and Wyckoff.  The smash-and-grabs take just a few seconds.

"We suspect they're using a center punch tool where they push it up against the window and give it a tap with a hammer and a metal rod shatters the glass," says Wyckoff Police Chief Ben Fox.

Members now say they will be more careful about leaving their pocketbooks in the car.

"There are lockers in the gym," says Sheri Rojas, of Ridgewood. "So I don't see a reason not to take it with you and lock it up properly."

Police are investigating to see if there is surveillance footage of the suspects.

Officers recommend putting valuables or bags in the trunk before driving to the gym.