Authorities in a southwest Ohio city say a house fire that resulted in a firefighter's death has been ruled arson.

Hamilton officials said Monday that the Dec. 28 death of 28-year-old Patrick Wolterman is now being investigated as a homicide. They declined immediately to discuss more details but urged the public to offer any information that could help their investigation.

Wolterman entered the smoke-filled home and died soon after falling through a floor into a basement. Firefighters learned later that the couple who lived there was away on vacation.

It was the first firefighter death in Hamilton in the line of duty since 1971.

Uniformed firefighters from across the country were among thousands of people who turned out Dec. 31 for a memorial service and funeral procession to honor Wolterman.