FONTANA, Calif. — Authorities in San Bernardino County are cracking down on the theft of what may look like trash but turns out to be treasure: cardboard.

Investigators at the district attorney’s office have been conducting sunrise surveillance to trail trucks piled high with flattened boxes heading to and from local recycling centers.

So far, they’ve issued two citations for petty theft in a bid to curtail the theft of cardboard from commercial bins, which is a source of recycling revenue for waste hauling companies.

People can collect and recycle cardboard but can’t remove the material from recycling bins.

David Biderman, general counsel for the National Waste & Recycling Association, said his industry loses millions of dollars a year due to cardboard theft.