WARSAW, Poland, March 25 (UPI) -- Authorities in Poland say two children were killed in an explosion of munitions left over from WWII battles, some of thousands that litter the country.
A 10-year-old boy and his 9-year-old sister were caught by the explosion as they played in a ditch in eastern Poland, The Daily Telegraph reported Friday.
The boy was killed instantly while his sister died at a hospital.
"The girl came to us in a very serious condition," hospital spokeswoman Agnieszka Osinska said. "She had multiple injuries including a severe head wound, and despite the best efforts of the doctors she failed to regain consciousness."
The children's mother and sister, who were nearby at the time of the explosion, were not injured, authorities said.
"I was not far away when I heard a huge explosion," witness Zdzislaw Milanowicz said. "My son thought it was a firework but I knew from my time in the army it was something like a grenade or a mortar shell."
It is thought the children may have discovered a grenade and somehow activated it.
"We've secured the area and found debris which we believe belongs to a Second World War grenade," Lt. Tomasz Dlugi of the Polish army's bomb disposal team said.
While Poland is littered with unexploded munitions left over from battles that took place all across the country during WWII, fatalities are rare, authorities said.