SIOUX FALLS, S.D. (KELO.com) — Sioux Falls Police says crooks are crawling under vehicles and cutting off the catalytic converters.

Officer Sam Clemens says the catalytic converters have some semi-precious metals in them.

They are then often sold on the internet.

Clemens says there were six reports of thefts over the weekend.

Over the past months, Clemens says there have been between 40 and 50 thefts.

He says they are hard to investigate as they don’t have serial or model numbers on them.

Clemens says if you see someone crawling under a car, call the police.

He notes that the thefts have been occurring all across the city.