Bystanders and firefighters worked furiously late Friday night to rescue residents of a St. Paul apartment building that was deliberately set on fire, officials said.

As a result of the quick action, no one was seriously injured in the blaze, which was reported just before 10 p.m. Friday. But St. Paul Fire Marshal Steve Zaccard said that police have launched an arson investigation.

No arrests have been made.

"When you set fire to an occupied building at 10 at night, you're trying to kill somebody. To me, that is attempted murder," Zaccard said. "People were asleep. People were relaxing."

Because the fire is under investigation, Zaccard declined to comment on reports that the fire was set just outside the building or that a domestic dispute involving one of the residents may have been a factor.

The building didn't sustain serious structural damage -- Zaccard estimated a loss of about $50,000 -- but smoke damage forced residents to leave. Some were taken by the Red Cross to a Roseville motel, while others stayed with relatives or friends.

Evidence of the fire was clear Saturday on the two-story, 11-unit building on Hamline Avenue just south of Larpenteur Avenue.

The brick front was smudged with smoke, the front door and windows were boarded up, and a sign with the large word "ARSON" was attached to the entry.

Two workers at the SuperAmerica station across Hamline may have been the first to notice the fire. Witnesses said they ran fire extinguishers across the street and directed them against flames surrounding the front door.

Two residents exited second-floor windows before firefighters arrived, apparently with the help of people on the ground, Zaccard said. One of them tied sheets together and slid down, he said.

Firefighters guided three residents down ladders from second-floor windows. A search of the building found two other residents, who were walked out the back door, Zaccard said.

Two residents were taken to Regions Hospital for treatment, but their injuries weren't life-threatening, he said.

Despite the fact that the building had no alarm or sprinklers, Zaccard said it was fully up to city code. Only three-story apartment buildings with at least 16 units are required to be outfitted with alarms, he said.

That no lives were lost is a credit to the firefighters, about 30 of whom responded to the blaze, he said.

"We're just grateful there were no more injuries or fatalities," Zaccard said. "So far there have been no fire fatalities this year; on average, we have three a year. There could have been fatalities last night."

Kevin Duchschere • 612-673-4455