All schools in the Bordentown Regional School District were expected to be open Friday, after a fire tore through the district bus yard early Thursday, damaging or destroying 11 buses and vans, a spokesman said.

Authorities have not determined the cause of the blaze, which left "hundreds of thousands" of dollars in damage and forced Bordentown to close four of its five schools for the day, authorities said. Transportation is provided to a majority of the district's roughly 2,500 students.

Bordentown Regional High, where many students drive to school, opened two hours late Thursday.

"It was very upsetting to see the damage and the destruction that occurred," District Superintendent Constance Bauer said.

The district expects insurance to cover the damage, Bauer said.

Officials said that all bus routes would be covered Friday and that schools would follow a normal schedule.

A motorist spotted the fire at Bordentown Regional Middle School on Dunns Mill Road, where the district keeps its fleet, about 3:35 a.m. Thursday, Bordentown Township police said. Damaged or destroyed were three of the district's 19 buses and half of its 16 vans.

Township police and state and Burlington County fire marshals are investigating the fire. Authorities encourage anyone with information to call Lt. Brian Pesce at 609-298-4300, Ext. 2129.