PRAGUE, Jumada Al-Awwal 16, 1432, April 20, 2011, SPA -- An official says a huge nitroglycerine explosion has occurred at a factory in the Czech Republic and that four people are missing. Wednesday's blast destroyed a building at the plant, which makes explosives for customers including the Czech military, and at least one person was injured, according to firefighter spokeswoman Vendula Horakova. The explosion occurred at about 7 a.m. (0500 GMT) at the Explosia AS plant in Pardubice, 100 kilometers (60 miles) east of Prague, the capital. The Associated Press quoted Harokova as saying that the cause of the explosion was not immediately known and that rescue workers with sniffer dogs are searching the site. --SPA 14:14 LOCAL TIME 11:14 GMT www.spa.gov.sa/885377