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
There are around 6,500 people in the UK waiting for a transplant. Some of them will be matched to a suitable donor. Sadly, many won't.
Turning colder, but mainly dry with sunshine.
Cold and frosty overnight. Dry, cold and sunny tomorrow.