The Vatican faced embarrassment on Tuesday after four kilograms of cocaine and 200 grams of marijuana was discovered in a car bearing diplomatic plates associated with the Holy See, the Guardian reported.

The car, which was stopped in order to be searched in France, belonged to 91-year-old Argentinean cardinal Jorge Mejia, emeritus librarian at the Holy See, who retired in 2003 and is currently bedridden after suffering from a heart attack.

Two days after being elected, Pope Francis had made a hospital visit to Mejia in Rome.

The cardinal's private secretary had reportedly entrusted the vehicle to two Italian men, aged 30 and 41, to take it for its annual checkup, French radio reported.

Instead they promptly drove to Spain, where they allegedly bought the cocaine. Believing the car's diplomatic status would place them above suspicion, and from there drove into France, according to RTL radio - a scenario not yet confirmed by legal sources.

The pair was picked up on Sunday at a toll station near Chambery in the French Alps en route back to Italy where police found the cocaine hidden in suitcases and bags, according to The Telegraph. Since neither of them had a Vatican diplomatic passport, the Vatican was not directly implicated, French legal sources said.

However, the men have been arrested and will appear in front of a French magistrate on charges of drug trafficking.

Although the incident was confirmed by the Vatican, it stressed that both men were Italian rather than citizens of the Vatican City State, and thus had no involvement with the Holy See.

"Cardinal Mejia is not well and obviously has nothing to do with this," said Federico Lombardi, the Vatican spokesman. "It's now up to the police to pursue their investigations."

In June, Pope Francis called addiction an "evil," warning of the dangers that taking drugs might create. He is firmly opposed to the legalization of any drugs, despite moves in many countries in the West, including several states in the U.S., to allow the personal consumption of soft drugs such as marijuana.

"I would reaffirm what I have stated on another occasion: no to every type of drug use. It is as simple as that," he told a drug-enforcement conference in Rome.

Drug trafficking "continues to spread inexorably," he said, adding it was fuelled by "a deplorable commerce which transcends national borders."