U.S. officials believe that Miguel Felix Gallardo, the fugitive drug trafficker wanted for the kidnaping and slaying of a U.S. drug agent last year in Mexico, has continued his flamboyant life style rather openly in Mexico and has spent an extended period as the house guest of at least one Mexican state governor.

One high-level federal official said that following the Feb. 7, 1985, disappearance of Enrique (Kiki) Camarena Salazar, an agent of the Drug Enforcement Administration, Felix Gallardo stayed at the estate of Antonio Toledo Corro, governor of the Mexican state of Sinaloa.

Another ranking U.S. official who has followed the Camarena case closely said Felix Gallardo also was a guest last year at the home of another Mexican state governor, whom he declined to name.

Toledo Corro said through a spokesman that he "does not know, nor has he seen" Felix Gallardo. Reports that Felix Gallardo has been his house guest are "inexact," he said.

Despite continued promises from the Mexican government that it is working diligently to capture and punish the persons responsible for the slayings of Camarena and a part-time DEA pilot, their handling of the case has strained U.S.-Mexican relations for the past year and severely frustrated U.S. Justice Department officials.

Federal law enforcement officials say they have been discouraged by continuing reports from informants of involvement by high-level Mexican police and politicians in the country's drug trade.

One U.S. official said he has been told that the Mexican government, to avoid scandal and embarrassment, will not move against any of the state governors who allegedly are involved in drug trafficking until after their terms expire in July.

President Miguel de la Madrid told U.S. officials that Mexican authorities could not take action against either governor without hard evidence, proof DEA investigators felt they couldn't provide without compromising Mexican informants, according to a U.S. source. De la Madrid's office had no comment, saying the allegations involved a local matter.

Toledo Corro said he "had no knowledge" of reports that Felix Gallardo recently had been seen publicly in Sinaloa and that the state government "is unaware that Mr. Felix Gallardo is legally considered a fugitive from Mexican justice, because this has not been communicated through legal channels."

However, Francisco Fonseca, chief spokesman for Mexico's federal district attorney's office, said in a telephone interview that federal authorities have issued "several warrants for Felix Gallardo's arrest relating to different offenses in different cities." Fonseca said that the warrants, accompanied by a picture of the fugitive, are routinely transmitted to all of Mexico's state police forces.

Camarena, a veteran DEA agent, was kidnaped from a busy Guadalajara street just outside the U.S. Consulate. Alfredo Zavala Avelar, the pilot, was abducted several hours later. The bodies of the two men, who had been tortured, were found last March on a ranch about 70 miles outside Guadalajara.

One U.S. official said that Felix Gallardo, one of the wealthiest men in Mexico, is believed to have stayed with Toledo Corro more than once and was seen in the Sinaloa area attending a wedding within the past 30 days.

"He has been seen frequently . . . in restaurants and other public places. He has also been seen with other officials. He's continuing his extravagant life style. They say he's still a high roller, very public, very visible to the public," said a high-level federal official in Washington. "But when we get the Mexican authorities to go after him, he's always gone. He's always tipped off."

Sinaloa, Felix Gallardo's birth place in northwestern Mexico, is in the center of the country's heroin production area, and Toledo Corro has been linked by a U.S. official and by local press reports to the drug trade. Culiacan, the Sinaloa capital, has won national attention during Toledo Corro's term as the city with Mexico's highest homicide rate, with most of the slayings remaining unsolved.

Toledo Corro has been criticized in the local press for not prosecuting reputed drug mob gunmen.

DEA Administrator John C. Lawn refused to comment on Mexico's handling of the Camarena investigation or the U.S. response.

But several sources confirmed that the Justice Department, frustrated with the slow pace of the Mexican investigation, has convened a grand jury here that has been taking testimony in the case for at least two months. The sources said several senior DEA agents here are assisting that investigation.

The grand jury has already heard testimony from Mexican drug trafficker Rene Martin Verdugo, who has been in U.S. custody since his arrest last month near the border in Calexico, Calif. Sources said Verdugo will be brought before the grand jury again soon.

A federal official said Verdugo was an associate of Rafael Caro Quintero, a major Mexican drug trafficker and suspect in the Camarena killing who is now in prison in Mexico. The sources said there is solid evidence that Verdugo was present when Camarena was slain. He has been charged with drug violations related to a 1983 marijuana case.

In a court hearing, Verdugo said he was kidnaped by six Mexican men, driven to the border and shoved through a hole in the fence where U.S. marshals were waiting for him. Afterward, the U.S. Immigration and Naturalization Service has confirmed, six Mexican men and their families were given special visas allowing them to remain in the United States for three to six months.

Verdugo's lawyers have filed a $110 million lawsuit against U.S. Marshals Service Director Stanley E. Morris, charging that the Mexicans who seized Verdugo were given $50,000 with a promise of another $50,000 when they delivered him.

Caro Quintero was captured only after he had left Mexico. He was arrested in Costa Rica last April by Costa Rican authorities acting on a DEA tip.

Shortly after the Camarena kidnaping, DEA agents alerted Mexican authorities that Caro Quintero was about to leave the Guadalajara airport on his private jet.

When they arrived at the airport with Mexican police, they discovered that the plane was surrounded by another contingent of armed Mexican police that allowed the plane to take off.

Armando Pavon Reyes, the Mexican Federal Judicial Police commander who led the investigation into Camarena's disappearance, later admitted to Mexican authorities that he had accepted a $275,000 bribe to allow Caro Quintero's plane to take off from the Guadalajara airport. Pavon is now in jail in Mexico City, but federal sources said they expect him to be released.