CIUDAD JUAREZ, Mexico — A boiler exploded at a candy factory in northern Mexico on Thursday, killing one person, injuring dozens and badly damaging the building, officials said.

They said at least one person was killed in the blaze at the factory which is located in an industrial park at Ciudad Juarez, a large city on the U.S. border.

"We're still searching the area to see if there are more dead," said Fernando Motta, head of the city's emergency services.

He said 11 people were badly injured, four of whom were in critical condition. Thirty people were treated for minor injuries, he said.

A second official, speaking on condition of anonymity, said around 20 people who work at the plant were unaccounted for. It was unclear if they were in the building at the time of the blast.