BALTIMORE — A fire that destroyed four buildings in Baltimore’s adult-entertainment area was started by a person and may have been deliberately set, fire officials said.

The five-alarm Dec. 6 blaze that ravaged The Block — a stretch of strip clubs, sex shops and other adult-entertainment merchants — was “set by human hands,” Deputy Fire Chief Raymond C. O’Brocki III, the city fire marshal, told The Baltimore Sun. “What’s not determined is the intent of the person.”

The fire is believed to have started in a video peepshow enclosure, known as Yellow Booth No. 8, at the Gayety Show World Book Store in a century-old building on East Baltimore Street, the newspaper reported Thursday.

It may have been intentionally and maliciously started by someone who was allowed to enter the adult bookstore or who slipped in through a backdoor, perhaps to get out of the cold, sources familiar with the investigation told the Sun.

Fire Chief Kevin Cartwright would not say whether an arson investigation was under way. Officials would not say whether they found accelerants.

The afternoon fire forced more than 20,000 city workers to evacuate buildings and snarled downtown traffic for hours. More than 150 firefighters battled the flames for four hours.