A freight train carrying construction material derailed in New Cassel Tuesday afternoon, causing LIRR rush-hour headaches that could extend to this morning's commute, authorities said.

Officials from the MTA and the Queens-based freight transporter, New York & Atlantic Railway, are investigating why the last two cars of a westbound, 16-car train went off the tracks at 1:10 p.m., just west of the Wantagh State Parkway. No injuries were reported, rail officials said, and determining the cause will take days.

The impact on the morning commute won't be clear until crews can get a full look at the track damage under the cars, said Aaron Donovan, spokesman for Metropolitan Transportation Authority.

A crane, which arrived Tuesday night, will be used to upright the cars -- an hourslong job, he said. Crews were working overnight to repair 200 feet of track and upright the two cars, he said.

By about 8 p.m. Tuesday, after the rush hour, regular service had resumed in both directions on all branches although there were residual delays, the LIRR said.

But earlier, with the derailed cars blocking one of two tracks between Westbury and Hicksville, riders on five of the 11 Long Island Rail Road branches -- Ronkonkoma, Port Jefferson, Oyster Bay, Babylon and Montauk -- felt the cancellations and delays.

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The LIRR dropped a third of eastbound, rush-hour trains and westbound service from Port Jefferson, Huntington and Ronkonkoma to Jamaica between 4 and 8 p.m.

A photo tweeted by the Long Island Rail Road showed a long freight car on its side on the grassy embankment, its wheels broken off. "Rerailing the cars is the hardest thing to do," Donovan said.

LIRR riders vented on Twitter with curses, talk of refunds and the "@LIRR strikes again."

"#LIRR delays and cancelations . . . not shocked any more #lirrfail," tweeted @jewlipina.

While it was not an LIRR train that derailed, a familiar theme emerged from riders -- not enough updates.

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Mike Levak, a Westbury engineer, said he found out mid-commute that his Ronkonkoma train would skip his home station, where his father was waiting without a cellphone, and go straight to Hicksville.

Levak said he wasn't made aware of the change until the train was in Mineola. "Had the LIRR told me just a little bit sooner my dad wouldn't have left for Westbury."

MTA officials said they updated train changes through Twitter, alerts and station announcements.

The derailment was the latest calamity for the freight railway, whose officials did not return calls Tuesday.

In July, one of its trains was hauling trash when it and a tractor trailer collided in Queens, prompting the Federal Railroad Administration to launch a probe into the railway's safety and operational practices. No one was seriously injured.

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A freight car carrying lumber in March derailed west of the Wyandanch station and crushed a portion of the LIRR's signal system. When parts of the system had to be made from scratch, commutes were affected by delays for days.In May 2014, part of a seven-car train went off the rails at the Jamaica transportation hub, but the freight railway's president said the cars remained upright and nothing spilled.