WASHINGTON — The government offered a $2 million reward Thursday for a Mexican drug kingpin known as "the friend-killer" as agents in three countries began arresting more than 100 members of his gang.

"I am confident that we will find him and bring him to justice," DEA Administrator Donnie Marshall said at a press conference to announce the move against the Mexican-led gang that smuggled tons of cocaine and marijuana into the United States.

Begun in October 1999, Operation Impunity II was the third major effort launched by the Drug Enforcement Administration since 1997 against the gang based in Reynosa and Matamoros, Mexico.

The gang's violent leader, Osiel Cardenas Guillen, stitched together remnants of two other gangs, formerly led by Amado Carrillo Fuentes and Juan Garcia Abrego, Marshall said.

"His capture is of paramount importance in this investigation," Marshall said. He noted that Cardenas Guillen has openly threatened U.S. agents and is known for purges of his own organization, which earned him the "friend-killer" nickname in Mexico.

"Those drug traffickers that threaten our agents can expect to be pursued and brought to justice, no matter what the cost in time or effort," he said.

DEA and FBI agents were arresting people in New York; Chicago; Columbus, Ohio; Memphis, Tenn.; Louisville, Miss.; and Houston, McAllen and Brownsville, Texas. By late afternoon, 57 people had been arrested, DEA spokeswoman Ila Brown said.

Eight U.S. provisional arrest warrants were given to Mexican police, who were trying to arrest key figures there. Another warrant was forwarded to the Dominican Republic for their police to arrest a Dominican national.

The Mexican attorney general's office announced the arrest of three Colombians, Ruben Dario Nieto Benjumea, Gustavo Adolfo Londono Zapata and Elkin F. Cano Villa, who were allegedly coordinating a cocaine shipment with Cardenas Guillen. The Mexicans also seized various property belonging to Cardenas Guillen in the northern state of Tamaulipas.

"Today's arrests are expected to have a substantial impact on the volume of drugs entering south Texas from Mexico for distribution throughout the United States," Attorney General Janet Reno said. "Operation Impunity II has been extremely successful in disrupting sources of supply of cocaine and marijuana and identifying both the foreign and domestic managers of this trafficking organization."

The State Department offered a $2 million reward for the capture of Cardenas Guillen or either of his two lieutenants, Adan Medrano and Juan Manuel Garza Rendon, in case they elude Thursday's dragnet in Mexico.

Prior to Thursday's raid, Operation Impunity II had made 82 arrests and seized $10.8 million in cash, 9,000 pounds of marijuana and 5,266 kilograms of cocaine, Marshall said. Overall, the three operations had produced 248 arrests and seized $36 million, 25,000 pounds of marijuana and 46,200 pounds of cocaine from 1997 through Wednesday.

"The rules of evidence force us to periodically take down parts of this operation, but the three operations show we're not stopping. We keep hitting them," said Joe Keefe, DEA chief of operations. "We've affected them, and forced them into new alliances to keep functioning."

Keefe said the investigation was continuing in other Midwestern and Western cities.

The gang smuggled cocaine from Colombia into the United States hidden under tractor-trailer loads of carrots, cilantro, lettuce, limes and jalapeno peppers, said Rod Benson, assistant special agent of the DEA's special operations branch. Sixty percent of each shipment was moved to New York and turned over to Colombian and Dominican distribution cells.

The other 40 percent was kept by the Mexican-led gang as payment for the smuggling operation and was shipped to their cells in Chicago, Houston, Memphis, Tenn., and Columbus, Ohio, for distribution by their own people, a DEA official said.

Cardenas Guillen was indicted, along with seven associates, in a U.S. Customs Service case in March in Brownsville on charges of conspiracy to distribute drugs and of assault on federal officers. The indictments were unsealed Thursday.

One assault charge involves a June 9, 1999 attack on an investigator working undercover for the Customs Service in Brownsville. The other charges grew out of a Nov. 9, 1999, incident at midday on the busiest street in Matamoros. A DEA agent and an FBI agent had been followed by a car through the city until a truck cut them off.

They were quickly surrounded by about a dozen men armed with AK-47 and AR-15 assault weapons and gold-plated .45-caliber pistols, Benson said. Cardenas Guillen stuck his head and a submachine gun into the U.S. agents' car and told them he would kill them. While the other armed men aimed their weapons at the car, the U.S. agents convinced Cardenas Guillen it would not be in his best interests to kill them.