The Washington Examiner reports that Virginia Railway Express spokesman Mark Roeber says 21 seats have been slashed. The service sent a message to its riders on Wednesday asking them to alert a conductor if they see someone slashing seats.

“We’ve been out there with staff and the Undercover Law Enforcement Officers but no luck so far,” the e-mail said. “Now, we ask you to help us keep watch during your commute to make sure we end this drama without any further sequels.”

Roeber says the seats cost $175 each to replace.

The newspaper says seat slashing is a common problem. Metro uses Kevlar, popularly known as the material used in bulletproof vests, in its newest bus seats.