PRAGUE (AP) -- A huge nitroglycerine explosion occurred at a factory in the Czech Republic on Wednesday, leaving nine people injured and four missing, officials said.
The blast destroyed one building at the plant and smashed windows in a large area around the facility, which makes explosives for customers including the Czech military, said firefighter spokeswoman Vendula Horakova.
Jaroslava Dolezalova, a spokesman at the Explosia AS plant in Pardubice, a town 100 kilometers (60 miles) east of Prague, said the blast occurred at about 7 a.m. (0500 GMT).
He said none of the nine injured were seriously hurt, but as rescue workers with sniffer dogs searched for the four missing people, authorities warned that further explosions were possible.
The powerful blast blew out windows in homes and shops in Pardubice and about four kilometers (2.5 miles) away in the town of Lazne Bohdanec.
Horakova said the cause of the explosion was being investigated.