A fire at a house where an adult and three children were found dead was the work of an arsonist, the Kansas State Fire Marshal's Office said Tuesday.

Chief investigator Rose Rozmiarek declined to say what evidence pointed to arson.

"It's still early in the investigation," she said.

The fire was reported Monday in the northeast Kansas town of Scranton, about 20 miles south of Topeka.

The names of the four victims would not be released until they have been positively identified and cause of death has been established by the coroner's office, Osage County Sheriff Laurie Dunn said.

The three children were under the age of 17, said Dunn, who declined to disclose their sexes or where their bodies were found inside the single-story house.

No arrests had made and nobody was in custody, she said.

Neighbors in the town of about 700 people said the well-kept home was occupied by a couple and their three children. Osage County tax records available online showed the house was owned by Michael L. and Amy C. Shirley.

Alicia Ambroski recalled that after she and her family moved next door in August, the Shirleys brought over muffins to welcome them.

"They were extremely friendly. You would have never thought anything like that would happen," she said. "We're playing it over and over again in our minds: What happened?"

The Kansas Lottery said a Scranton man identified as Michael Shirley won a $20,000 prize in a drawing last year and in 2007 won $8,600 in cash and merchandise in a drawing.