By David DeKok
HARRISBURG, Pa. (Reuters) - The discovery of a cache of cannon balls left behind after the worst civilian disaster of the U.S. Civil War brought construction on a Pennsylvania apartment complex to a halt on Tuesday while workers waited for the ordnance to be removed.
At least 20 cannon balls were unearthed on Monday in Pittsburgh by a contractor on the site of the former Allegheny Arsenal, where a Sept. 17, 1862 explosion killed 70 mostly teenaged workers.
There were too many cannon balls for the Pittsburgh Bureau of Police's bomb disposal unit to remove so a specialty firm from Maryland was called in to clear the site, said Sonya Toler, a spokeswoman for the Pittsburgh Department of Public Safety.
"They should be on the site today to begin the work," Toler said in an interview.
Officials believe the cannon balls are stable, but have posted a 24-hour police guard on the site, Toler said.
Workers had been alerted of the possibility that ordnance would be found, and stopped when the first cannonball turned up in the bucket of a excavator.
Many of the victims of the arsenal were torn apart and burned beyond recognition by the blast, which killed the 13-year-old daughter of one of the plant's supervisors, who had worked on the production line.
The disaster took place on the same day as the Battle of Antietam, which stands as the deadliest one-day battle of the war that led to the abolition of slavery in the United States.
(Editing by Scott Malone and James Dalgleish)