Dylan Beto, 3, chattered happily as he was released, John Beto said, and was "doing really well. . . . Thank goodness someone is." Dylan was treated at Christopher's Hospital for Children in Philadelphia for minor injuries.

His siblings, Mikayla Beto, 2, and Anthony Claxton, 6, died in the fire that swept through the family's home in the 400 block of Park Avenue on Sunday.

Their mother, Kristy Beto, 22, was listed in critical but stable condition yesterday in the burn unit at Temple University Hospital.

"Preliminary indications are that the fire was caused by a child playing with matches in the house," said Montgomery County First Assistant District Attorney Kevin R. Steele. "We believe it was the 6-year-old."

Investigators had feared arson because police found a gasoline can on the front lawn, but John Beto said he was having problems starting his car and bought the fuel because he thought he might have run out of gas.

Shortly before noon Sunday, passersby called 911 to report an explosion and smoke coming from the residence. Within minutes, emergency workers found Kristy Beto suffering from burns after unsuccessful efforts to reach her children.

Firefighters did reach Mikayla, but she was pronounced dead at Phoenixville Hospital. Anthony was dead at the scene, police said. A neighbor, Thomas Gamble, rescued Dylan Beto, police said.

"I came home and saw my whole house in flames," said John Beto. "A friend of mine, who's a police officer . . . came over and said, 'We lost one.' "

Beto said his son, Eddie, who also lives at the home, had stayed overnight in Pottstown with friends. "Otherwise, he would have been here," said John Beto. "He's taking it pretty hard."

Yesterday, yellow police tape surrounded the charred two-story yellow frame home. Police Chief Barton K. Bucher said the fire was being investigated by multiple agencies, including Montgomery County detectives and state police.

Windows were boarded up, but reminders of the children's activities dotted the lawn: a stroller, a scooter, a bike and balls.

A couple who did not know the family stopped by to add a bouquet of roses to a makeshift memorial near the curb.

Trish Caufield, accompanied by her husband, John, shook her head sadly, explaining that the children's ages reminded her of their own grandchildren.

"I just hope the community gathers around," she said.

Asked whether anyone had contacted him with offers of assistance, John Beto said a fund had been set up at the Citizens Bank office on West Ridge Pike in Norristown "in loving memory of Anthony Claxton and Mikayla Beto."

He said he had not been able to communicate much with his daughter, who is still on a ventilator, but when he tried to tell her "it's going to be all right," she shook her head.

"She knows those kids didn't make it," he said, his voice cracking. "I'm sorry, that's what hurts the most; it's very hard right now."