An alarm sounds off throughout a Fort Jackson construction site alerting crew members that in just 60 seconds the area would erupt in explosion.A man shout outs 'Fire in the hole, fire in the hole!' Afterwards white smoke scatters in the sky right above the fenced off enclosure on Hampton Parkway.In just a couple of months, this location will house hundreds of initial entry Soldiers attending Basic Combat Training at Fort Jackson's newest battalion, but up into now, unknowingly to anyone on post, this site has been serving as a hidden home to a Vietnam-era weapon; the white phosphorus hand grenade."We're really not sure how the grenades ended up in this location," said Eric Jones, project manager for the construction site. "We have some theories, but nothing is for sure."A controlled detonation took place Sept. 29 on Fort Jackson to remove the grenades from the grounds of the construction area. Jones said he expects more of these weapons will be discovered as construction progresses."We have 11 acres of land to work on and who's to know what we'll dig up as we keep working," he said.The grenades were first discovered in July during the excavation phase of construction. During the excavation, white smoke rose from the area alerting crew members that something was wrong."I was actually at another construction site and I could see all the white smoke going up in the air. I thought it was a fire at first," said Jones. "We immediately called Fort Jackson's (Explosive Ordnance Disposal company) and firefighters."After a surface sweep of the area, Fort Jackson's EOD unit found roughly 55 grenades and safely disposed of them at an approved range on post. White phosphorous grenades are dangerous because they are known for "burning to the bone." White phosphorus will continue to burn until it is completely gone.Since Fort Jackson's EOD unit is only equipped to handle emergencies, experts from Huntsville Center's Military Munitions Design Center arrived to do a subsurface clearing where they found four more grenades."We had to do an air burst," said Tom Meeks, Ordnance and Explosives Safety Specialist from the Design Center."When white phosphorus is exposed to air it completely blows up. If we blow it up on the ground, it would just stay in the ground and keep exploding which wouldn't be good.This is the best way to deal with it."The grenades found on the construction site are about 60 years old, according to Jones."I've worked on many military sites, but have never ran into this," he said. "There's been training aids, other explosive, shell cases and different inhabitants, but not white phosphorous."