Sparrows Point implosion.

Workers at Sparrows Point imploded one of the buildings at the closed steel plant Friday, causing a loud boom that was heard in nearby Dundalk, Baltimore County Police said.

MCM Industrial Services conducted a controlled demolition of the Basic Oxygen Furnace shop building at 2 p.m. on Friday, said Cpl. John Wachter, a Baltimore County police spokesman.

The steel mill at Sparrows Point, which employed tens of thousands in its heyday, closed in 2012 after its last owner, RG Steel, filed for bankruptcy.

Another furnace, the L blast furnace is set to be destroyed sometime this summer, according to Hilco Global, the firm that is carrying out the liquidation of the plant. A Star of Bethlehem that adorns the top of the furnace — a nod to the plant's former owners Bethlehem Steel — will be removed and given to the neighboring community.

"We are currently working through the best way to take the Star down to preserve it," said Gary Epstein, chief marketing officer for Hilco. "Given its size and its fragile state, it my require thousands of dollars of work just to preserve it before removing it, likely by helicopter."

timswift@baltsun.com