There were reports of eight to 10 people hurt at the New Hampshire Ball Bearings Inc. plant, Peterborough Assistant Town Administrator Nicole MacStay said. Emergency crews from multiple communities were called, and a decontamination site was set up, she said.
Bill Brock, owner of the Manhattan East Hair Design shop about a quarter-mile from the plant, said he heard and felt something but didn't know what it was. Then about 30 ambulances and fire trucks went by.
Gov. Maggie Hassan said the state emergency operations center was open to monitor the situation. Police advised drivers to avoid Route 202 through Peterborough, a town of about 6,000 residents in the southwestern part of the state.
Local hospitals were asked to prepare for patients who may have been exposed to hazardous materials.
A message seeking comment was left with the company, which has its corporate headquarters in Chatsworth, Calif.