LANCASTER - Authorities yesterday said they have no suspects in the weekend killings of a couple and their teenage son in their suburban home and pleaded with the public to help them solve the crime.

Thomas Alan Haines, 50; his wife, Lisa Ann, 47, and their son Kevin, 16, were found stabbed to death Saturday in their two-story stone house on a leafy street in an upper-middle-class neighborhood of Manheim Township, police said at a news conference.

"Someone knows something about this crime," Chief Neil J. Harkins said.

Authorities repeated a warning to residents to keep their doors locked.

The couple's daughter Margaret, 20, was home at the time and called 911 from a neighbor's house at 2:24 a.m., police said. She was awakened by a noise and went into her parents' bedroom, Harkins said. Her father was lying on the bed and her mother, who was sitting on it, quietly asked her daughter to go get help, Harkins said.

Margaret, known as Maggie, did not see a suspect or intruder, he said. *