One Amtrak worker was killed and two people were reported injured in an explosion in New York City on Thursday, authorities said.

The Amtrak employee had been working on an electrical line when the blast occurred in the Bronx, authorities said. The NYPD responded to a 911 call on the explosion just after 11 a.m.

Police had initially reported that a transformer had exploded, before NYPD Chief of Department Terence Monahan said the employee was killed while working on an electrical line.

Amtrak immediately halted several trains coming in and out of the city's Pennsylvania Station. By about 1 p.m., trains appeared to be moving again.

Amtrak spokesman Jason Abrams said the national rail operator has launched an investigation.

"We are deeply saddened to report the death of an Amtrak employee," Abrams said in a statement. "The incident happened at approximately 11:05 a.m. at a substation just outside of New York City. There are reports of two additional non-life-threatening employee injuries."