Lozoya, a close ally of Mexican President Enrique Pena Nieto, became Pemex CEO in December 2012, overseeing the company during a momentous energy reform that ended Pemex's decades-long monopoly over the country's oil and gas sectors.

Earlier on Monday, two Pemex spokesmen said Lozoya was working normally in his office and denied he was leaving.

It is not clear who will replace Lozoya, but one of the sources and local media have said that Jose Antonio Gonzalez, the current director of Mexico's Social Security Institute, would take his place.

Mexico's presidential office said it would hold a press conference at 4 p.m. on Monday, but gave no explanation what it would be about.

Pemex has been suffering from the rout in global oil prices and over a decade of declining production, posting record losses and being forced into drastic cost-cutting measures.

Mexican Finance Minster Luis Videgaray, who is said to enjoy a frosty relationship with Lozoya, said on Monday that Pemex's board would announce fresh budget cuts in the coming days due to the slump in oil prices.