A roof collapse at a construction site in Franklin Township Friday left two workers hospitalized, one seriously injured and another with less severe injuries.

Nine construction workers were on top of the roof when the truss collapsed just after 2 p.m. at the site on Worldfair Drive. Authorities say the building under construction will be a medical arts center.

One person has been rescued from the scene after being trapped in the collapse.

Investigators for the Occupational Safety and Health Administration arrived at the scene shortly after to investigate the collapsed.

Witnesses reported hearing an ?unearthly? sound and many went running to the scene. One eyewitness, a construction supervisor on another project, said roofs can sometimes collapse because trusses are insufficiently supported.