TEHRAN, Iran — One person has died and four others were injured on Thursday after an explosion at an Iranian university laboratory, according to local media reports.

It is believed the blast was caused by a hydrogen capsule at Tehran University’s engineering and technical college, in the Amirabad neighborhood of the capital, Tehran, several news outlets reported, citing Tehran fire department spokesman Jalal Maleki.

Witnesses said they heard a loud explosion near a laboratory at the college.

Maleki said the explosion caused a fire, but the situation is under control and the case is under investigation.

Tehran has been scene in recent months of fire and explosions that were mainly blamed on gas leakages and electrical short circuits.