One man was taken to Maine Medical Center after a fire started Saturday evening in a two-unit apartment building on Woodford Street in Portland, fire officials said.

Portland Fire Chief David Jackson said the man, a tenant in one of the units at 179 Woodford St., was taken to the hospital largely as a precaution. The man was walking out of the building with his dog when firefighters arrived at the scene shortly after 6 p.m. The dog did not appear to be injured, Jackson said.

No other tenants were home at the time of the fire, he said, and did not arrive while firefighters were on the scene.

Jackson said fire officials don’t know how the fire started, but the most intense flames when they arrived appeared to be in an area above the second-floor apartment and below the roof. He said firefighters will be investigating the cause, assisted by Portland Police Department crime scene technicians.

Jackson said those technicians were called because they can take high-resolution images of the fire and the aftermath, not because the fire is considered suspicious.

Nearly an hour after firefighters arrived, smoke was still coming out of the building and occasional flames could be seen coming from the roof. Two firefighters on a ladder were hacking at the roof with axes and firefighters inside the building on the second floor were directing the spray from their hoses on the underside of the roof.

By 7:30 p.m., the fire appeared to be mostly out.

Jackson said none of the firefighters was injured, even though a paramedic was seen taking the blood pressure and measuring the pulses of many of them. Jackson said that is a new procedure his department follows after firefighters emerge from a building that was on fire, and wasn’t due to Saturday’s heat.

Temperatures neared 90 degrees in Portland on Saturday, but it had cooled considerably by the time the fire was reported Saturday evening.

Some firefighters loosened a valve on the side of a tanker truck and doused themselves with water after coming out of the building.

The fire was in a building set back from Woodford Street, near Woodfords Corner. It was behind a much larger apartment building that appeared undamaged.

Jackson said fire officials hope to determine the cause of the fire Saturday night or Sunday.

He said the building was not habitable, although it may not be a total loss.