St. Louis Park Police reported 18 thefts since November.

GOLDEN VALLEY, Minn. — No matter the time of day, a parked car is vulnerable.

"Just a complete shock," Alex Rudelius of Golden Valley.

She parked her Honda Odyssey overnight in South Minneapolis a few days ago. The next morning she got behind the wheel.

"It was just really loud," said Rudelius. "Drove it right to the shop to see what was going on."

Her catalytic converter which connects the tailpipe to the engine was stolen.

Steve Larson at Muffler Clinic and Brakes in St. Louis Park took care of it.

"They could do it for little under 500 dollars," said Rudelius.

Rudelius isn't the only one to take her car there with the part stolen.

"Seen a dozen or more in the last two or three weeks," said Larson.

At least two police departments have seen an uptick in these thefts. St. Louis Park says there's been 18 thefts the past several weeks. Minneapolis Police say they've seen an increase as well.

Steve says the reason thieves target them is the metals inside.

"Those metals are very valuable and the cores can be sold at different types of places that buy them," said Larson.

St. Louis Park posted on Facebook some prevention steps including: