Army bomb disposal engineers were called into a building site in the southern Polish city of Krakow after workers unearthed more than 200 unexploded anti-tank mines from World War Two. Builders working on a new halls of residence building for the city’s famous Jagiellonian University were forced to down tools on Wednesday after one of their diggers hit the hoard. Over the next two days, investigators found the ordnance, most of it unused anti-tank mines, as well as “a substance of unknown origin,” police said. Two sacks containing around 60 kilograms of powder were found, a senior specialist firefighter told TVP Krakow. He also said the mines contained no detonators. The area was cordoned off as a precaution, and army sappers removed the items to neutralize them safely, a police statement said. Work at the site has been suspended until a specialist company can come on Monday to make sure the site holds no further alarming surprises. A police spokesman said the site had been inspected by specialists several years ago and several dozen unexploded devices had been found. He added that the area was used as a military training ground until the 1970s.