Two people are in critical condition following an explosion at a ball bearing plant in southern New Hampshire. 

Several first responder vehicles were called to the scene to deal with the emergency at the New Hampshire Ball Bearing plant in Peterborough. 

Authorities say up to 15 people were injured by the explosion, which was felt up to a quarter-of-a-mile away. 

Fire officials released a statement saying there was no known fire and the cause of the blast is under investigation. 

A spokesperson for the company says about 700 people work at the plant but she didn't know how many were there at the time of the blast. (Metro Networks Inc.)