An empty New Jersey Transit train derailed early Wednesday in Manhattan’s Penn Station, causing some delays at the beginning of the morning rush hour.

An Amtrak crew was moving a New Jersey Transit train out of a railyard around 5 a.m. when some cars derailed on Track 4, where repair work started earlier this summer, according to NJ Transit spokeswoman Penny Bassett.

The derailed cars were cleared by 6:20 a.m.

NJ Transit’s Northeast Corridor, North Jersey Coast, Montclair-Boonton and Midtown Direct trains initially had 20-minute delays but were back on schedule quickly. The Long Island Rail Road and city subways were not affected, according to New York’s Metropolitan Transportation Authority.

A linchpin in the northeastern U.S. rail system, Penn Station, which is owned by Amtrak, is undergoing accelerated repair work to replace several thousand feet of track, switches and other aging infrastructure. The speedup was prompted by two derailments in the station during the spring that wreaked havoc on rail service between Boston and Washington, D.C.

More than a half million people pass through Penn Station daily on New York City subways and trains run by Amtrak, NJ Transit and the LIRR.

Before the work began, New York Gov. Andrew Cuomo warned that commuters could be in for a “summer of hell,” but he’s since eased off that prediction.

(AP)