MEXICO CITY -- A federal money laundering investigation of Roman Catholic Cardinal Juan Sandoval Iiguez has reignited long-smoldering allegations of links between drug money and the Catholic Church.

When President Vicente Fox recently flew Sandoval to his ranch on a government helicopter for a family party, it added fuel to one of Mexico's hottest scandals in years.

"It is very well known that in many parts of the country drug money is given to the church. . . . The drug dealers are like philanthropists," said Roberto Blancarte, a Mexico City scholar who specializes in church-state relations. "The question is, should church leaders take the money, knowing where it comes from?"

The precise allegations against Sandoval have not been made public, but Attorney General Rafael Macedo de la Concha confirmed that the cardinal is under investigation after Reforma newspaper reported that Sandoval's bank records were being subpoenaed.

Government prosecutors have long alleged, without disclosing specific names or amounts, that drug traffickers have given large donations to church leaders who were secretly baptizing their babies and attending their birthday parties. Movies and songs here have often touched on this connection, most recently in the hit movie, "The Crime of Father Amaro."

Some of the allegations against Sandoval involve his years in Ciudad Juarez, a border city with a thriving drug trade, according to daily press reports about the scandal. He now presides over the church in Mexico's second largest city, Guadalajara. Several thousand supporters, including members of Congress, marched in the streets last weekend on his behalf. They carried banners that read: "I believe the cardinal."

Sandoval, 70, an outspoken conservative who sits on a committee that oversees Vatican finances, has said he has done nothing wrong and that the campaign against him is a vendetta by a former federal attorney general.

Editorials in Catholic newspapers, a prominent group of bishops and many parish priests speaking during Sunday Mass have criticized the investigation. The overall message, according to Blancarte, is the church saying: "'Don't mess with us."

The Catholic Church has been an enormously powerful institution here since the Spanish introduced it 500 years ago. In an effort to curb its influence, political leaders attempting to modernize Mexico in the early 20th century enacted some of the world's toughest laws separating church and state. Until 1992, Catholic priests and nuns were not allowed to vote or wear their clerical garb in public. Although all Mexican presidents have been Catholic -- as are about 90 percent of Mexicans -- they kept their worship private.

With his election in 2000, Fox became the first president to openly embrace his Catholicism. He raised an image of the Virgin of Guadalupe, Mexico's patron saint, at a campaign rally, and was subsequently fined for breaking electoral rules prohibiting the use of religious symbols. After his election, Fox took communion at a Mass with television cameras rolling, and kissed the ring of Pope John Paul II, who has frequently traveled here.

Fox spokesman Agustin Gutierrez Canet said today that the president has maintained a "very clear separation of church and state" on the Sandoval matter, despite the use of a government helicopter to ferry Sandoval to Fox's ranch on Sept. 21. Gutierrez said that on that day, Fox's mother, Mercedes Quesada, a Catholic, was celebrating the feast day of the saint who bears her name.

Gutierrez said that Fox respects the rule of law and that "there will be no exceptions for the church."

Still, many analysts expressed surprise that the president would meet with a man under federal criminal investigation, and to do so at government expense. Sandoval told reporters that Fox promised him a swift investigation. Gutierrez said Fox did not promise Sandoval any special treatment.

Nightly updates on television news programs have shown pictures and video of the cardinal with the wealthy "czar of gambling," Jose Maria Guardia, who reportedly owns horse racing tracks and gambling parlors in several states. Officials in the attorney general's office have said their investigation also involves Guardia, as well as a congressman from Fox's political party and other members of Sandoval's family.