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WASHINGTON (CBSMiami/AP) —The feds say they did not find that five airlines were involved in price gouging after a train derailment in 2015.

The Transportation Department told the airlines their investigation found they did not take part in any wrongdoing.

Transportation Secretary Anthony Foxx announced last year that the department was investigating whether American, JetBlue, Delta, United, and Southwest airlines raised airfares for flights between major airports in the corridor extending from Boston to Washington following a May 2015 Amtrak train derailment.

Eight people were killed and about 200 injured in the derailment in Philadelphia, disrupting Amtrak service for days. Thousands of Amtrak passengers were forced to make other travel arrangements at the last-minute.

The department quietly sent letters to the airlines recently saying the investigation found “no evidence of unfair manipulation of airfares or capacity, nor evidence of unconscionable increases in fares beyond normal pricing levels.”

The letter from Blane A. Workie, DOT’s assistant general counsel, said that an examination of over 5,000 pages of data involving 76 flight segments in the Northeast corridor concluded that although airfares did increase on many of the routes after the derailment, they also decreased on some routes.

Sen. Christopher Murphy, D-Conn., had complained to the Obama administration at the time that at least one airline was charging as much as $2,300 for ticket following the derailment.

Matt Miller, a spokesman for American Airlines, said the carrier was gratified by DOT’s finding and had been confident that no wrongdoing would be found.

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