'Bolt Banging Syndrome' Likely Cause For Evacuation At Lexington School

LEXINGTON (CBS) -- The loud boom that shook Estabrook Elementary School in Lexington Thursday morning was likely caused by the normal movement of structural bolts, authorities said.

The condition, known as Bolt Banging Syndrome, occurs when bolted joints held in place by friction slip into bearing under load. The design allows for parts of the building's structure to expand or contract, which normally happens in new buildings during seasonal changes.

Lexington police talked to parents and staff outside the high school field house after the evacuation. (WBZ-TV)

The school was evacuated about 9a.m. after a loud bang was heard and the ground shook. No one was hurt. School was dismissed for the day.

Inspectors ruled out any mechanical, electrical or gas problems in the building.

School resumed Friday morning.