MEXICO CITY, December 10 (Reuters) – The commercial arm of Mexican state oil company Petroleos Mexicanos (Pemex) has temporarily suspended business with Vitol, according to a letter seen by Reuters, amid an investigation into US bribes to oil trading firms.

As part of a wider investigation, the US Department of Justice said last week that a US subsidiary of Vitol, the world’s largest independent oil trader, paid bribes to employees of Pemex (PEMX.UL) in exchange for lucrative contracts.

The department said Vitol’s US unit had agreed to pay $164 million to complete a US government investigation into alleged bribes the company paid in Mexico and other Latin American countries.

In a letter seen by Reuters and dated Wednesday, Pemex’s PMI Comercio Internacional said it had “taken the decision to temporarily suspend commercial relations” with the Vitol company.

Pemex and Vitol did not respond to requests for comment.

Mexican President Andres Manuel Lopez Obrador said Thursday that his government would investigate the allegations.

“This is being investigated and if true, those responsible will be punished. We are not covering anyone up,” he said.

The bribes allegedly took place during the administration of Lopez Obrador and under Mexico’s previous president, Enrique Pena Nieto, according to Mexican newspaper Reforma.

The Swiss company Vitol, out of London, trades about 8 million barrels of oil per day.

Reporting by Stefanie Eschenbacher in Mexico City; Additional reporting by Julia Payne in London and Raul Cortes Fernandez and Adriana Barrera in Mexico City; Edited by Angus MacSwan and Edmund Blair

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