Emergency services stand on the site of a Bosch plant. Two men die in a gas explosion on the Bosch site. 

Emergency services stand on the site of a Bosch plant. Two men die in a gas explosion on the Bosch site. Bernd Wei?brod/dpa

Two men were killed in a gas explosion at German engineering firm Bosch's facility on Tuesday morning in the south-western city of Reutlingen, according to police.

A 52-year-old man died at the scene of the accident, while his 44-year-old colleague succumbed to serious injuries in hospital, police said. Both were reportedly employees of an external company doing work for Bosch at the facility.

According to the police's findings so far, silane gas leaked from a gas cylinder that was attached outdoors, although the cause of the leak was initially unclear. Silane gas is used for calibration.

Warning systems were activated by the leak, but when employees went to investigate the cause, the gas reacted with the air and exploded.

The two men were nearby and were caught in the explosion, while another worker suffered from blast trauma.

Police are investigating the incident and seeking to determine the precise cause of the blast, but said there is no longer any danger to the public.

Emergency services stand on the site of a Bosch plant. Two men die in a gas explosion on the Bosch site.