There were no immediate reports of injuries, local media said. CBS3 TV in Philadelphia, citing unidentified sources, said a man was holding his girlfriend and another woman hostage inside the facility.
"UPS is working with law enforcement as they respond to an active shooter situation at one of the company’s supply chain processing facilities in Logan Township, New Jersey," UPS said in a statement.
An officer answering the phone at Logan Township police would confirm only that a SWAT team had been dispatched to the scene, which is about 25 miles (40 km) southwest of Philadelphia.
"We do have an incident," he said. "Other than that, I don't have any information."
CBS3 said Logan Township police confirmed that shots had been fired at the scene during the incident, which began at about 8:30 a.m. EST (1330 GMT).Officials in Gloucester County, which includes Logan Township, said 32 employees were inside the facility at the time of the incident, and that the building was subsequently evacuated, CBS3 reported.