(Reuters) -A unit of global commodities trader Trafigura has agreed to pay a $55-million civil fine to settle U.S. Commodity Futures Trading Commission charges of fraud, manipulation and impeding whistleblower communications.

Trafigura Trading LLC, a Houston firm that is part of Trafigura Beheer BV, violated U.S. law and regulations by trading gasoline with material nonpublic information, by manipulating an oil pricing benchmark and by requiring current and former employees to sign agreements that barred them from sharing company information, including with regulators, the CFTC said in a statement.

The agreements with employees illegally impeded them from voluntarily communication with the CFTC's enforcement staff during their investigation. The charge marked the first time the CFTC has brought an action against a firm for impeding whistleblower communications, the regulator said.

Trafigura, which neither admitted nor denied the CFTC's findings, said it has voluntarily sought to boost its compliance program and has agreed to modify its non-disclosure provisions in employment and severance agreements.

From 2014-2019, Trafigura traded gasoline while possessing material nonpublic information it knew or should have known was misappropriated from a Mexican trading firm, regulators said.

The firm in February 2017 also manipulated a fuel oil benchmark to benefit its futures and swaps positions, the CFTC said.

(Reporting by Costas Pitas and Ismail Shakil in Washington and Chris Prentice in New York; Editing by Aurora Ellis)