More than a dozen steelworkers were injured when a coke oven blew up at a Nippon Steel & Sumitomo Metal Corp. factory in Tokai, Aichi Prefecture, police said Wednesday.

An emergency call at about 12:30 p.m. said that “a coke oven exploded” at the Nagoya steel plant, forcing the entire workforce to be evacuated by around 2 p.m. Three of the injured had serious wounds.

Although no fire appeared to follow the explosion, the city asked nearby residents to stay indoors while plant officials determine what happened.

The Nagoya plant has been plagued with problems this year. On four occasions, power failures caused large plumes of black smoke, a problem the company is also busy trying to address.