Police are responding to an active shooting at a UPS facility in New Jersey, the company said Monday.

"We are working with law enforcement as they respond and cannot provide information about the identity of people involved at this time," UPS said in a tweet.

An employee at the facility in Logan Township, about 20 miles (32 kilometers) south of Philadelphia, said he heard an apparent gunshot and began to run.

Allen Anthony Dowling tells The Associated Press he heard a fellow worker say someone had a gun. Dowling says he then heard what he thought was a gunshot and began to run along with other employees.

Police surrounded an area around a loading dock at the supply chain processing facility. Television news footage showed armed officers crouching behind one of the vehicles.

Schools in the area were put on a modified lockdown.