PORTLAND — A property owner was acquitted Friday of manslaughter in a building fire that killed six people but was convicted of a code violation in converted attic rooms described by prosecutors as “death traps.”

Gregory Nisbet was found not guilty of the most serious charges of manslaughter, which carry a penalty of up to 30 years in prison. He was also acquitted of some lesser charges but was convicted for not having adequate means of escape from third-floor rooms.

The case was widely watched in Maine, where no landlord has been successfully prosecuted for manslaughter because of poor building conditions.

The fire, which was blamed on improperly discarded smoking materials, swept through the apartment house early on Nov. 1, 2014, after a Halloween party.

Prosecutors said Nisbet’s building, which was in foreclosure, lacked working smoke detectors, adequate exits and other safety measures. The defense contended the state tried to hold Nisbet to a higher safety standard by classifying the home as a boarding house.

The fire killed Nicole Finlay, David Bragdon Jr., Ashley Thomas and Christopher Conlee, along with Topsham resident Maelisha Jackson. Rockland resident Steven Summers was hospitalized and died two days later. Several others were able to escape.

The fire was determined to be an accident: It was started by smoking materials on the porch.

But prosecutors argued that the victims would’ve escaped if not for the landlord’s negligence. The screams of three victims trapped in the third floor indicated they were alive and would’ve survived if they had been able to get out of the building, they said.

Those rooms were “death traps,” prosecutors said, because they lacked a second way to escape in the event of a fire.

Prosecutors said Nisbet had stopped maintaining the building and vetting tenants during foreclosure. Conditions had gotten so out of hand that some people were living temporarily in the cellar or even outside using extension cords for electricity, prosecutors said.

The case was decided by Justice Thomas Warren after Nisbet waived his right to a jury trial. Several family members were on hand for the verdict.