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.
On Monday, some residents of Apatzingan showed their continued support for Nazario Moreno.
Around 300 people took part in what was originally billed as a peace rally.
Some held up signs supporting Mr Moreno, whose La Familia cartel is feared for its ruthlessness, but which also claims to protect local communities, and to promote religious and family values.
Mr Moreno is widely considered to be its ideological leader. He was the author of a book known as The Family Bible that was used to train new recruits.
La Familia Michoacana is involved in cocaine smuggling to the US along Mexico's Pacific coast as well as the production of the synthetic drug, methamphetamine.