MEXICO CITY, Mexico: The governor of Mexico's Sinaloa state, Ruben Rocha Moya, returned to office this week after taking more than three months away from his duties following US drug trafficking charges. His return is likely to increase tensions between Mexico and the United States.

Rocha, 77, is a member of Mexico's ruling Morena party. In a statement posted on X, he said he was returning to his duties with a clear conscience and his head held high.

The move is a major turnaround for Rocha. He has so far avoided extradition to the United States and has now returned to the governor's office.

His return has added another chapter to a case that has tested security cooperation between the US and Mexico. It has also highlighted the difficulties in the relationship between the two countries. Despite years of joint efforts to fight drug cartels, Mexico remains strongly opposed to US actions that it believes threaten its national sovereignty.

Public policy expert Martin Castillo of the University of Chicago said the Mexican government was willing to extradite drug traffickers if the US requested it, but appeared less willing to extradite members of the political party led by Mexico's president.

However, signs suggested that Mexican President Claudia Sheinbaum and the Morena party had not welcomed Rocha's return.

Rocha said Mexican authorities had found no evidence supporting the allegations against him. He also claimed that the US case was politically motivated and aimed at Sheinbaum's left-wing political movement.

Morena said in a statement that it had not known about Rocha's decision beforehand and distanced itself from his return.

Mexico's interior ministry also said Rocha made the decision alone. It added that an investigation by the attorney general's office into Rocha and others accused by the US was still ongoing.

A US State Department spokesperson did not respond to questions about Washington's reaction to Rocha returning to office.

The spokesperson said the Sinaloa Cartel sends deadly drugs to the United States and has been classified as a terrorist organization. The spokesperson also said the cartel could not operate without help from corrupt officials.

In April, US prosecutors accused Rocha and nine other current and former Mexican officials of working with Los Chapitos, a faction of the Sinaloa Cartel. Prosecutors alleged that the officials helped the group traffic drugs into the US in return for political support and bribes.

The case was unusual because US anti-cartel action had expanded beyond drug traffickers to include a senior serving Mexican politician. Washington has often accused Mexican politicians of having links to organized crime, but Rocha is the first sitting Mexican governor to face charges in the United States.

The allegations increased tensions between the two countries, which are close allies. Mexican authorities began their own investigation into Rocha in early May. At the same time, Sheinbaum described the US case as foreign interference and increased her calls for Mexico to protect its national sovereignty.

Mexico has since said that Washington had not provided enough evidence to justify Rocha's arrest or extradition.