Anhydrous ammonia is stored as a liquid under pressure, but becomes a toxic gas when released, according to health officials.
Neighbors reported smelling an odor near the company building around 7:30 a.m., FOX43 in York reported.
EAST PALESTINE RESIDENT POSTS PHOTOS OF RESIDUE ON WALLS, SAYS HOUSE 'REEKS' OF CHEMICAL SMELLS
HazMat officials said the shelter in place order was in effect for residents within a half mile range of the Kunzler Meat Company in Lancaster, Pennsylvania. (Google Street View)
No injuries were reported.
HazMat teams places air sampling devices throughout the neighborhood to monitor the plume of anhydrous ammonia. (HazMat 2 Environmental Fire Rescue Company)
EAST PALESTINE TRAIN DERAILMENT TAKES CENTER STAGE AT SENATE HEARING
Officials warned residents to stay indoors while HazMat teams set up devices to take air samples throughout the area.
No further details were immediately available.