Police have given no explanation for the blast Sunday evening at the Galenika pharmaceutical factory on the outskirts of the Serbian capital.
Authorities have advised residents to stay indoors to avoid breathing in any toxic fumes.
Hospital officials say the injured include 20 firefighters, seven factory workers and two policemen.
Most are expected to be released from the hospital later Monday.
Güncelleme Tarihi: 07 Nisan 2008, 14:26