Bill Knaper of Washington and Dowling General Contractors prepares a track hoe before starting demolition at 593, 595 and 597 W. Princess St., which burned over the weekend. (Bill Kalina photo)

A weekend fire that destroyed three buildings at the corner of West Princess and South West streets was deliberately set.

York City Fire Chief Steve Buffington said a state police fire marshal determined an arsonist set the three-alarm blaze.

Crews responded to the fire about 11:30 p.m. Saturday, he said. It was well involved when the fire department arrived, Buffington said.

All three houses at 593, 595 and 597 W. Princess St. were vacant, and no one was injured, he said.

The buildings are part of the Salem Square Project, a neighborhood initiative by the YMCA of York County, the city and several other groups, to restore houses.

"It's very disappointing," said Larry Richardson, president and CEO of the local Y. But "we won't be discouraged."

Demolition: A city public works crew pulled down portions of the buildings damaged by the blaze for safety reasons Sunday morning, said Kevin Schreiber, the city's economic and community development director.

The buildings will be completely demolished Monday, said Jessica Fieldhouse, director of community development with the YMCA.

That's a little ahead of a previously planned schedule. The buildings were to be razed in the next couple of months, she said.

"Instead they are coming down tomorrow," Fieldhouse said.

Once the buildings are torn down, grass will be planted until officials determine what to do with the lots.

What will become of the three lots has yet to be decided. But Fieldhouse said she's hopeful three vacant corner lots in a part of the city that is undergoing rehabilitation could entice private investors to build new houses there.

"With three vacant lots ... reuse can be whatever the market allows," she said.

Fire: The fire went to a third alarm for additional manpower. The whole rear portion of two of the houses collapsed, Buffington said.

There was some heat damage to a nearby home at 143 S. West St., and the homeowners are temporarily displaced while repairs are made, he said.

Firefighters remained at the scene through the night putting out hot spots. They didn't leave until about 10:30 a.m. Sunday.

The buildings have a combined assessed value of $49,120, according to county tax records.

Previous fire: Saturday's blaze wasn't the first arson in one of the three buildings.

In January 2010, a fire broke out at 595 W. Princess St., which was vacant at the time. It also damaged an adjoining property at 597 W. Princess that then served as the York City Police West Princess Resource Center.

That blaze undermined the structural integrity of 595 and 597 W. Princess Street.

"That's what was preventing us from refurbishing them in the first place," Richardson said.

Anyone with information about Saturday's fire is asked to call York City Police at 846-1234, or call the city's anonymous crime tip line, 849-2204. Or anonymously text a tip to YORKTIPS at 847411.

- Reach Greg Gross at 505-5434, ggross@yorkdispatch.com, or follow him on Twitter at twitter.com/YDcrime.