But in a stock exchange filing, Brazil's state-run oil company said there were "no negotiations taking place about partnerships" with the US-based oil major.
Mexico's state oil company has disclosed four contracts it signed with the disgraced Brazilian engineering firm as it assists the attorney general's office with its investigations.
Leftist ruling party candidate Lenín Moreno was the winner of Sunday's vote, but former banker Guillermo Lasso has alleged foul play and is challenging the results.
International companies land contracts for urea and propylene projects.
Natural gas has more than doubled its share of the Latin American power matrix since the early 2000s, and is used to generate more than a quarter of the region's annual electricity supply.
With the liberalization of fuel imports and the retail segment in Mexico, fuel prices will drop to similar levels to those in Texas within a couple of years, according to Beau Freyou, director of Houston-based IVG Energy.
US producers allege that biodiesel imports from Argentina surged 464% from 2014-16, due to "illegal trade activities." The Argentine exporters' chamber says the allegations are unfounded.