Police in the southwestern German city of Reutlingen said a gas cylinder had started leaking silane gas outdoors at about 0700 GMT on Tuesday when several workers went to investigate.
The company said two employees of a contractor were killed by the explosion, and another was lightly injured.
"We are deeply saddened by the death of the two employees of the external company. Our thoughts are with their families," a spokesperson said in an email.
Investigations are underway to determine the reason for silane gas leak, the company said.
