Service on the Clinton-to-Mukilteo ferry route was halted for more than 30 minutes Monday due to “damage” of the Mukilteo terminal’s apron.

Service stopped around noon and resumed shortly after 12:30 p.m.

The lack of service left vehicles stuck on the ferry as the arriving vessel had to wait for repairs to the terminal. Washington State Ferries officials say passengers on the route should expect delays through the afternoon rush hour.

The cause of the damage remains unclear. A statement from Washington State Ferries says the Mukilteo terminal’s apron — the ramp that extends from the terminal to a ferry to allow loading and unloading — was damaged, but agency officials don’t yet know how.

Hadley Rodero, spokeswoman for Washington State Ferries, said it’s under investigation. It could take weeks before a cause is determined.

Full service has since resumed. Temporary weight restrictions and single lane loading and offloading were in place until about 2 p.m.

“Temporary weight restrictions are now lifted on the Mukilteo/Clinton route and normal loading and offloading procedures are in place,” according to the agency statement. “The route will continue service on a load and go schedule until further notice. Updates will follow as more information becomes available.”

Rodero said it isn’t clear when two lane loading and unloading will resume, or when the temporary weight restriction will be lifted.

For updates, visit http://www.wsdot.wa.gov/ferries/vesselwatch/terminaldetail.aspx?terminalid=5.

The halted service comes at a bad time for the agency. Spokesman Ian Sterling said the agency currently has “zero backup vessels at the moment,” due to a vessel issue in the San Juan Islands.

“We’re down a vessel in the San Juans, which is causing them great concern,” Sterling said. “We’ve already lost one more boat than we can afford to lose during a busy summer season. We’re stretched as far as we can be.”