Mexican president Felipe Calderon says plans by a notorious drug cartel for an extravagant party led to the killing of its leader.
Nazario Moreno of the La Familia Michoacana cartel was killed in a gun battle with police last week.
Mr Calderon says police had learned of the cartel's plan to hold a party for hundreds of people and the gun fight broke out when they arrived to investigate.
They are still searching for his body.
The authorities say they believe members of the cartel have retreated into the mountains of Michoacan and have taken the body of Mr Moreno, known as "the Craziest One", with them.
President Calderon said the killing of Mr Moreno was the biggest blow the authorities had inflicted on the cartel in its history.
"With a certain amount of insolence, they organised a party, a gathering of hundreds of their people," he said.
He told Mexican radio that "everyone had found out about the party", prompting the authorities to send hundreds of police officers and soldiers to the town of Apatzingan, a stronghold of La Familia.
Police say five of their officers were killed during the massive operation, as well as three alleged members of the gang and three civilians. BBC News
