The United States has no plans to return a Mexican doctor brought across the border by bounty hunters to face charges of participating in a drug agent's murder, officials said Thursday. Mexico's request for the return of Dr. Humberto Alvarez Machain was received by the State Department and the U.S. will ``respond in due course,'' Justice Department spokesman Doug Tillett said. However, officials who spoke on condition of anonymity noted that Mexico had not made a formal extradition request, calling merely for Alvarez's return. The officials also pointed to recent public statements by the Justice Department stressing that the U.S. had no plans to return Alvarez to his homeland. Justice Department spokesman David Runkel said several weeks ago that he couldn't ``foresee any circumstances'' under which Alvarez would be returned. Alvarez, accused of participating in the torture and murder of Drug Enforcement Administration agent Enrique Camarena, was abducted by bounty hunters and flown to El Paso, Texas, on April 3. His arrest by waiting DEA agents touched off a diplomatic flap between the two nations that included a charge by President Carlos Salinas de Gortari that it violated Mexico's sovereignty. Attorney General Dick Thornburgh said in a May 10 interview, however, that he was not concerned about the circumstances of Alvarez's delivery to the U.S. border. He invited bounty hunters to turn over more Mexicans wanted in the Camarena case. ``Whatever actions that are carried out by Mexican authorities are of no moment to us,'' Thornburgh said. The Mexican Foreign Ministry said in a statement issued Wednesday in Mexico City that the government wanted Alvarez's return for questioning about possible crimes in Mexico. The statement did not mention specific cases. ``This request is based fundamentally on the fact that the procedure followed by his captors and those who transferred Dr. Alvarez Machain violated'' articles of the Mexican constitution, the statement said. Alvarez is scheduled to appear in U.S. District Court in Los Angeles on Friday for a hearing on defense motions to dismiss the charges because the circumstances of his arrest amounted to ``outrageous government conduct.'' Last week, the Justice Department filed papers claiming that a Mexican police official last year delivered an offer to swap a suspect in the Camarena case for a fugitive wanted by Mexican authorities. The papers quoted the Mexican official as saying he was speaking on behalf of Mexican Attorney General Enrique Alvarez del Castillo. The Mexican attorney general has since issued a statement denying the Justice Department claim. Antonio Garate Bustamante, a former Mexican police official residing in Los Angeles, has said he arranged Alvarez's abduction for DEA.