Eight people were killed in an explosion at a Denel munitions depot near Somerset West on Monday afternoon, the City of Cape Town's fire and emergency services spokesperson said.
"The City's Fire and Rescue Service responded to Rheinmetall Denel Munitions Factory at 15:45," said Theo Layne.
"On arrival it was ascertained that an explosion had occurred...
"Four persons are confirmed to have sustained fatal injuries and firefighters are currently carrying out search and rescue for a further six persons."
He said the cause of the explosion has not been ascertained as yet.
So far 15 firefighters and three fire engines were at the incident.
When News24 called the company's offices, understood to be a few kilometres away from the blast, a person who answered the phone said the CEO would issue a statement later.
According to its website, Rheinmetall Denel Munition (Pty) Ltd was established on September 1, 2008 when the Denel divisions Somchem (Somerset West and Wellington sites), Swartklip, Boksburg and Naschem (Boskop site), became part of the Rheinmetall Defence Group.
The company became known as Rheinmetall Denel Munition (RDM).