The Mexican attorney general"s office (FGR) said on Monday it was investigating two leading opposition gubernatorial candidates in the northern border state of Nuevo Leon ahead of June mid-term elections, citing campaign irregularities. Adrian de la Garza from the Institutional Revolutionary Party (PRI) is being investigated for vote buying and Samuel García from the Citizen Movement party is being probed over allegedly suspect campaign financing, FGR said in a statement. Garcia and de la Garza are 16 and 11 points ahead of Clara Flores, the candidate from the ruling MORENA party of President Andres Manuel Lopez Obrador, according to a poll in the Reforma newspaper. De la Garza is being investigated for courting the female vote with an electronic "pink card", which allows voters to withdraw money "once the candidate wins the election", FGR said in a statement. De la Garza could not be immediately reached for comment. One of the complaints against Garcia is by the finance ministry"s Financial Intelligence Unit over alleged electoral crimes in the funding of his campaign, including contributions suspected of coming from "funds or goods of illicit origin". Garcia denied any wrongdoing and said he would appear before authorities to respond to any accusations as he does not have anything to hide. "There are no irregularities in my campaign and much less in my personal or professional life. The only thing I"m guilty of is riding high in the polls," Garcia said on Twitter. Lopez Obrador last week referred to the alleged purchase of votes by the PRI"s de la Garza in Nuevo León, and said that electoral authorities were clueless about what was happening in the campaign. Nuevo Leon, a wealthy industrial region and a key border state, is seen as one of the most prized gubernatorial seats up for grabs on June 6. Fifteen of Mexico"s 32 states will elect a new governor on that day.