A fire burns at the Philadelphia Energy Solutions refinery hours after a series of early morning explosions at the 150-year-old industrial complex at 3100 W. Passyunk Ave. (Emma Lee/WHYY)

Feds to investigate Philly refinery explosion as local health experts remain cautious

Philadelphia Energy Solutions is the largest refinery on the East Coast and the single largest source of air pollution in Philadelphia
By Susan Phillips, Steph Yin, WHYY and Jake Blumgart, WHYY