A thick cloud of smoke hung over downtown Charleston this morning as firefighters extinguished a blaze that began in the rear of the Old Towne Grill and Seafood restaurant next to The Riviera building.

The fire, first reported at 8:08 a.m., is being ruled as accidental, according to Mark Ruppel, the public information officer for the Charleston Fire Department.

Olde Towne owner Spiro Fokas had contracted with crews to work on the roof of the building Tuesday morning. The crews arrived about 7 a.m., and used power tools to cut a hole in the roof. When they left the site to pick up supplies, the fire started.

The fire spread to the attic of the small cinderblock building where crews had begun work, Ruppel said. Firefighters were on the scene by 8:10 a.m., parking a ladder truck in front of the Riviera and battling smoke and flames in the back.

There was a little external scorching, but no significant damage to The Riviera, said Paul Stracey, general manager of Charleston Place, which is the owner of The Riviera building.

The restaurant, which opened in 1972 at 229 King St., is across from Charleston Place. Athan Fokas, the son of the restaurant's owner, said no one was due to work at the restaurant until 9 a.m.

Jeremy Wellman was among the first to call 911. A worker at Sweetgrass Cafe on Market Street, he smelled smoke in the air when he stepped outside to take break.

"It smelled like something was burning," he said. "There was no visible smoke at first. Then, all of a sudden, billowing black smoke start pouring out."

Wellman and other witnesses reported hearing popping sounds. "It sounded like firecrackers going off."

Liz Harrison, who works at neighboring City Lights Cafe, said it sounded to her as though windows were breaking in the business as the fire grew.

The building is one of three tenements constructed in a row by businesswoman Rachel Lazarus around 1839, according to Jonathan Poston's "The Buildings of Charleston." Lazarus, who was in the dry goods business, constructed the three-story buildings with a loan from the city after the great fire of 1838, Poston's book states.

Firefighters also battled the heat of the day, as they drank water provided by the Charleston Place hotel. Downtown traffic was snarled while firefighters battled the blaze and police blocked off King Street from Wentworth Street south.