50 firefighters are tackling a blaze at G&P Batteries on Willenhall Road, Walsall.
ITV News Central has been told by eyewitnesses that a number of loud explosions could be heard at the plant.
It is the second time this year a fire has broken out at the factory - the previous one on 14 January saw 60 firefighters in attendance.
More top news
East Midlands weather: Breezy with clear spells
West Midlands weather: Windy with some showers
From Princess Charlotte's shawl, to commemorative mugs, find out how the Midlands has welcomed the latest addition to the royal family.