The problem started because they began to use the money for illegal things.
For example; in 2004, Raúl Muñoz Leos signed an agreement in an illegal way with the Syndicate of Petroleum Workers of Mexico. This agreement forced PEMEX to give almost 8 millions pesos to the Syndicate of Petroleum Workers of Mexico. According to Raul Muñoz, Carlos Romero Deschamps, leader of the union, forced him to sign this agreement.
Another example, the largest, was that in 2001, it was discovered that funds from the workers union of PEMEX, the national oil company, were misdirected to support the campaign of Francisco Labastida, the gubernatorial candidate for the Institutional Revolutionary Party in the year 2000. Those thought responsible were not convicted although the party was fined $1,000 million (about USD$90 million). The press gave it the name 'pemexgate', a portmanteau of PEMEX and Watergate.
In 2001, investigations started and after a large process, the government declared that Pemexgate was not a matter of money laundering or organized delinquency. Because of this, many people were declared innocent but some of them where declared responsible for electoral fraud and illegal exercise of the public trust.
There were people from PEMEX that were declared innocent: Rogelio Montemayor (ex director of the administrative corporative), Carlos Juaristi Septien (ex director of the financial corporative), and Julio Pindter Gonzalez (subdirector of labor relations).
From the union, three men were declared innocent of money laundering and organized delinquency, but they were accused of electoral fraud and illegal exercise of the public trust: Carlos Romero Deschamps (leader of the union), Ricardo Aldana (union member), Jesus Olvera Mendez (union member).
From the PRI, four men were declared innocent from money laundering and organized delinquency, but they were accused of electoral fraud. It is important to mention that they were collaborators (directly involved in the campaign) of Francisco Labastida. They were: Carlos Aldama (ex secretary of elections), Jorge Cárdenas Elizondo (ex secretary of financial department), Alonso Bretón Figueroa (sub secretary of financial department), and Joel Hortiales Pacheco (ex technical secretary of financial department).
Mexican and international journalists do not want to cover Pemexgate or for that matter uncover it for fear of their death.