Francine Mykich was preparing S&S Candy and Cigar Co. for its busiest day of the week when she thought she heard a truck hit the South Side store.

“We came in just like a normal Monday morning, and then all of a sudden ka-boom,” said Mykich, who has worked at the business on East Carson and South 21st streets for 26 years. “We came outside, and it’s been steadily crumbling.”

A wall of the building, which dates to 1892, collapsed onto 21st Street about 8:40 a.m. Rubble covered the sidewalk and part of the street. All the employees safely evacuated the building, and no one was injured.

“The time of day was very fortunate,” Mykich said. “We weren’t open yet, thank God.”

The collapse likely was caused by moisture freezing between layers of brick and breaking the bonds between them, said John Jennings, the city’s interim building inspection director. When the bricks thaw, there’s nothing left holding them together, he said.

The owner of the building, identified in property records as Richard Stephens, has to get an engineer to stabilize the building before clean-up begins, Jennings said. Bricks and pieces of the building continued to fall throughout the morning. Through employees, Stephens declined to comment.

It could take a day or more to stabilize the building, Jennings said.

The building is part of the East Carson Historic District. It first appeared as Armour & Company Wholesale Meats in 1892, said Frank Stroker, assistant archivist with Pittsburgh History & Landmarks Foundation.

“It was probably their main facility at that point,” Stroker said.

Armour held the location until 1952. The building then briefly became home of Freezer Foods Inc., Stroker said. By 1956, Brinn’s China and Glassware moved in, he said, and held the spot until S&S took over in 1965.

City officials would have to approve any demolition, alterations or repairs because of its location in the historic district, said John Martine, an architect and member of the local advisory committee to the city’s Historic Review Commission.

Martine said he’s always admired a canopy along the side of the building. The collapse destroyed the canopy.

“It was a very simple, but interesting canopy with wonderful wood brackets that went the length of the loading docks,” Martine said. “It’s a very working-type building. It’s not that fancy, but there’s enough detail there that it would be a loss to see the building go.”