WILL COUNTY, Ill. (WGN-TV) A suburban Illinois school district was forced to hold an emergency e-learning day after the catalytic converters were stolen from nearly all of its buses.

The Troy 30-C School District, which has schools in Joliet, Plainfield and Shorewood, said in an announcement to parents Monday morning:

“This unfortunate act has rendered the majority of our buses inoperative, despite the implementation of robust security measures, including surveillance cameras, enhanced lighting, and secure fencing.”

School officials first estimated that “over 90%” of buses were affected, but reduced the number to “over 80%” in an afternoon update.

They believe the thefts happened early Monday morning and the suspected vehicle is a dark-colored SUV. The vehicle passed the intersection of Riviera Blvd. and Leonard Drive in Joliet between the hours 3:00 a.m. and 3:15 a.m.

“On this day students will complete assignments from home, and they will not come to school,” the school said.

As of Monday afternoon, officials were still trying to determine whether or not in-class instruction could resume on Tuesday.

The district said they are actively working with Joliet police and with their bus vendors to expedite repairs.

“We sincerely appreciate the patience and understanding exhibited by our community during this challenging time. Continuous updates will be provided throughout the day as new information emerges,” the district said.

Catalytic converters have been targeted in recent years because thieves are able to get money for them at scrap yards, thanks to the precious metals they contain.