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.
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Rain may be heavy in places but should clear to sunny intervals and scattered showers later in the day.
Rain quickly spreads from the west, turning heavy over the higher ground. Sheltered eastern spots will escape the worst of the rain.
Marcus Willis, a current club coach ranked 772 in the world, came through six qualification matches to reach this year's tournament.