The underground blaze that caused temporary disruptions at Penn Station in Manhattan early Tuesday has been ruled accidental, fire officials tell NBC 4 New York, rolling back initial FDNY assessments that the cause of the fire appeared to be suspicious in nature.

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More than 150 firefighters battled the three-alarm fire that took over two levels of a construction site by the west end of the LIRR concourse at Penn Station at West 33rd Street and Eighth Avenue, FDNY Chief James Leonard said.

The blaze initially appeared to be suspicious in part because of its location in the heart of midtown, but fire officials said later Tuesday it was an electrical fire that started near temporary wiring used for lighting the construction site.

A firey blaze delayed trains coming in and out of Penn Station early Tuesday morning, according to the FDNY. Credit: @___ninoblak___/Instagram.

The fire caused substantive structural damage to the station, according to the FDNY. Tracks 19-21 for LIRR trains into Penn Station were not affected by the fire but they were shut down to assist in the investigation. Track 19 later reopened but tracks 20 and 21 remained closed Tuesday afternoon.

Off-peak LIRR service was not affected and full LIRR service was in effect for the evening rush.

The blaze, which started just before 2:30 a.m., caused A and E trains to temporarily bypass the station. Subway service returned to normal by 5:30 a.m., though some residual delays lingered throughout the morning.

The investigation also closed several roads in the area. Two firefighters were hurt battling the flames but are expected to be OK.

Empire State Development, the city's chief economic development agency, which runs the site where the fire broke out, says construction should resume at the pace it's been rolling and the first phase of the project is on target for completion in August 2016.

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