MEXICO CITY (AP) _ A suspect in the killing of a Roman Catholic cardinal said after his weekend arrest that he and another gunmen fired at the prelate because they thought he was a rival drug lord, authorities said Monday.

The statements by suspected gunman Edgar Nicolas Mariscal support the government's theory that Cardinal Juan Jesus Posadas Ocampo was killed by accident when his vehicle was confused with that of a drug lord.

Mariscal's arrest and testimony should help the government close the murder case, one of three major assassinations in recent years. Still unsolved are last year's murders of the ruling party's original presidential candidate and the party's No. 2 man.

Failure to clear up the killings has dogged President Ernesto Zedillo, whose government also faces a severe economic crisis, a smoldering rebellion in southern Mexico and growing demands for political reform.

Mariscal was picked up on Sunday in the Pacific coast state of Sinaloa following several days of surveillance, the attorney general's office said in a statement.

He was riding in a pickup truck in Los Mochis, about 750 miles northwest of Mexico City, carrying a machine gun and 20 cartridges, the statement said.

When authorities took him in for questioning, he reportedly admitted that he and fellow gunman Juan Francisco Murrillo Diaz fired at the cardinal's white Gran Marquis sedan because he thought it was that of rival drug lord Joaquin Guzman Loera of the Sinaloa cartel.

The Attorney General's Office identified the primary gunmen in the cardinal's slaying as Mariscal and Murrillo, who was killed in an August 1994 shootout with federal agents in Sinaloa.

The largely Roman Catholic nation was stunned when Posadas, his chauffeur and five others were slain by machine-gun fire during a May 24, 1993, shootout at the airport in the western state capital of Guadalajara.

The government said that the gunmen, hired by Tijuana drug cartel bosses, mistook the cardinal for Guzman, who was also at the airport.

Guzman was arrested soon afterward and held in a high security prison outside the nation's capital. The Tijuana drug bosses remain at large.

The general public and the church hierarchy have long been skeptical of the government's theory in the case.

A high-ranking government source told The Associated Press in March that new leads had been discovered in the Posadas case and that a new theory focused on a ``premeditated assassination.''

No arrests were made in connection with a premeditated murder and the government quickly returned to its original theory of a man killed because of mistaken identity.