By Neil Offen

noffen@heraldsun.com; 419-6646

DURHAM -- Investigators now believe a fire that ravaged the Royal Oaks apartment complex last week and injured a firefighter was caused by arson.

Fire Department officials initially said they weren't sure what had caused the blaze that started in the basement of a 20-unit building at 3545 Mayfair St.

But Sierra Jackson, a spokeswoman for the department, said Monday that investigators are now looking into the likelihood that the fire was intentionally set.

"That's what's they're investigating now," Jackson said. "That's the basis they're working on."

The fire, which damaged 10 units and displaced 14 adults and six children, began early in the morning and kept crews at the scene for more than three hours.

It was the third fire at the apartment complex in the past three years.

But Jackson said the three fires do not appear to be related.

She said the first fire, which happened in the summer months of 2006, was deemed accidental while the second fire, which occurred last month, is being treated as arson.

A juvenile was charged with setting the Oct. 6 fire.

Jackson said the department was not releasing any more details about the most recent blaze since officials didn't want to jeopardize the ongoing investigation.

The firefighter injured last week fell into the basement through a hole in the first floor, but was not injured seriously, officials said.