Updated at 7:44 p.m.

A 19-year-old worker who was trapped when a mineral silo collapsed early Monday in the Ashburn area had not been found by evening.

Emergency crews worked through the afternoon to stabilize a silo at Luck Stone Quarry.

Officials had halted the search late Monday morning to wait for heavier machinery to aid in the search. The effort was expected to resume in the evening.

The collapse happened about 6:30 a.m. at the quarry off Belmont Ridge Road. The business said the federal Mine Safety and Health Administration was aiding in the search, along with the Loudoun County Sheriff’s Office.

Engineers and riggers worked with cranes to stabilize the silo, said Loudoun County Assistant Fire Chief Keith Johnson. The silo’s contents, a flourlike mineral filler used in asphalt and road construction, is dangerous to inhale, he added.

“We’re really concerned that removing one bit of product can cause the whole silo to fall,” Johnson said.