Twelve people were injured on Monday from an explosion at a factory owned by defense company Rafael Armament Development Authority. The firm said the accident occurred at its David Site plant in Haifa and appeared to be the result of a faulty battery in a diesel engine that was located in an enclosed area. Initially, there were fears that the explosion was the result of a terrorist attack, but it soon became clear it was a work accident. Police and fire crews arrived at the site minutes after the blast, but were barred from accessing the security-sensitive compound. Only later did officials permit a bomb expert and a small team of policemen to enter the area where the explosion occurred. Police said the detonation caused a roof to collapse at the plant, but the company declined to provide further details about the accident. Two workers were taken to hospital in serious condition while ten others were injured lightly. A permanent Magen David Adom team located at the site immediately began treating the wounded at the plant's clinic, after which they were evacuated to the Bnei Zion, Carmel and Rambam hospitals in the Haifa area. Rafael chief executive and president Yedidia Ya'ari has appointed a committee to investigate the incident, while officials from the Ministry of Trade, Industry and Labor and detectives from Zvulun region police will also carry out a probe. A company official said the explosion was the first at the plant in recent years. In 1992, two workers were killed and 47 injured at an explosion at the Israeli Military Industries facility near Nof Yam. An investigating committee found that carelessness, a series of human errors and an unavoidable chain of tragic events caused the accident. Rafael, which is state-owned, develops high-tech defense systems for air, land, sea and space applications and has customers all over the world. Its products include air-to-air missiles, ceramic bullet-proof vests and propulsion systems for micro- and mini-satellites.