More than 30 catalytic converters were stolen from school buses at two lots in East Hartford over the weekend, according to the East Hartford Police Department.

The converters were stolen from First Student at 68 Alna Lane and Autumn Transportation at 52 Oakland Ave. sometime between Friday and Monday, police said.

First Student said 12 catalytic converters were stolen from its lot on Alna Lane and its bus operations were not impacted by the thefts. Its maintenance team is working to repair the affected buses, according to First Student spokesperson Jay Brock.

No arrests have been made in the investigation. Detectives are reviewing surveillance video and other evidence, police said.

Autumn Transportation provides school bus transportation to Wethersfield and Hartford Public Schools and and CREC magnet schools, according to its website.

Catalytic converter thefts have sharply risen in popularity over recent years since they can be stolen quickly and sold for high prices on the illicit market for the precious metals they contain, according to the National Insurance Crime Bureau.

“Catalytic converter theft takes minutes to complete and is easy to conceal,” said Trooper Sarah Salerno of the Connecticut State Police. “They are located beneath the body of a vehicle and their absence generally isn’t noticed until someone starts the vehicle and hears loud rattling or roaring noises or smells unusual exhaust odors. In some instances the vehicle’s check engine light will illuminate.”

A catalytic converter is a piece of a car’s exhaust system. It helps reduce toxic gases and pollutants from a vehicle’s exhaust, according to AAA.

On Jan. 10, Torrington Public Schools were forced to delay school for two hours after catalytic converters were stolen from 10 buses around 2:30 a.m. that day, according to Torrington Chief William Baldwin.

There are ways for drivers to protect against catalytic converter thefts. There are anti-theft devices available for purchase that drivers can install to help secure the part to a car. The NICB also recommends parking personal vehicles in a garage or installing motion sensor lights if a driver must park in a driveway.

Salerno recommended that drivers inscribe their car’s VIN number or state and license plate on the converter with heat-resistant paint. She also recommended drivers check with their insurance company to ensure a theft would be covered under their current policy.

Victims of catalytic converter theft should contact the police and their insurer once they find out their converter has been stolen, the NICB said. A catalytic converter replacement can cost anywhere from $1,000 to $3,000 typically, depending on the converter needed and the shop a driver uses to repair it, the NICB said.