LANCASTER - Authorities said they had no suspects in the weekend stabbing deaths of a couple and their teenage son in their home and pleaded with the public yesterday to help solve the crime.

Thomas Alan Haines, 50; Lisa Ann Haines, 47; and their son, Kevin, 16, were found stabbed to death Saturday in their house on a 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.

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 seek assistance, Harkins said.

"Her mother said to her to go get help, leave the house and go get help," the chief said.

Margaret, known as Maggie, did not see an intruder, he said.

Officers arrived minutes after receiving the 911 call and found the three victims dead inside the two-story stone house. The parents were in their bedroom, and the son was in a hallway.

Autopsies showed they died of stab wounds. Harkins said no weapon was recovered.

"Who the hell did this?" Lancaster County coroner Gary Kirchner said. "I mean, that neighborhood is a class neighborhood."

Authorities again warned residents to keep their doors locked. Police found the Haineses' back door open when they responded to the 911 call. Harkins would not say whether that was how the killer entered, but he noted that there were no signs of forced entry and that nothing was taken from the home.

The search warrant for the home was sealed, Lancaster County District Attorney Donald Totaro said.

A next-door neighbor, Leonard Witkonis, described the Haines family as quiet. "They weren't very sociable," Witkonis, 68, said.

At Manheim Township High School, where Kevin Haines was a sophomore and member of the German club and Quiz Bowl team, a moment of silence was observed yesterday.

"Everybody is kind of in shock," said Marcie Brody, a district spokeswoman.

Maggie Haines was a 2005 graduate of Manheim Township, according to Brody, and had just completed her sophomore year at Bucknell University. She returned home Thursday, Harkins said.

Totaro said Maggie Haines has cooperated with investigators, and Harkins said investigators had no reason to believe she was involved in the killings.

Thomas Haines was a salesman at Motion Industries in Lancaster. Lisa Haines was a teacher at Lancaster Brethren Preschool, according to Jeffery B. Rill, pastor at the Lancaster Church of the Brethren.