The explosion occurred about 12:30 a.m. Sunday in the old cast shop, which is in the Northwest quadrant of the plant, said plant manager Art Pepper this morning.

There were four people working in the cast shop at the time, he said.

They reported that while pouring molten metal, which contained a copper beryllium alloy, the machinery malfunctioned and continued to pour when it should have stopped, Pepper said.

The metal came into contact with water, which caused steam and the explosion, he said.

Plant officials as a courtesy contacted the sheriff's office, Ottawa County Emergency Management Agency and the Ohio Environmental Protection Agency.

Pepper said, however, that the incident was classified as a Level 0, which means there was no requirement to contact the outside agencies.

Plant workers conducted air sampling in the building after the incident and it indicated there was no detectable traces of beryllium, Pepper said.

The workers also tested the outside air on the plant site to make sure nothing was released, but those results are not back yet, he said.

"Since there were none in the building, that would lead us to believe we will see similar results from the outside air tests," Pepper said.

Brush Wellman processes beryllium, a metal that in dust form can cause those who are sensitive to it to develop chronic berylliosis disease, which can result in death.