Then, shortly before midnight, a white double-cabin pickup screeched to a stop on Palm Tree Street in the town of Navolato. At least four gunmen burst from the vehicle and sprayed the party with semiautomatic gunfire.

Eight people were killed, among them women and teenagers. Several more were seriously wounded and remained hospitalized Sunday, said Jose Luis Leyva of the state prosecutor's office in Culiacan, the state capital about 20 miles to the east.

The shooting may have been part of a string of apparent vigilante attacks in which low-level criminals have been killed by armed squads thought to be working with drug traffickers, police -- or both. More than 30 carjackers and robbers have been killed in similar circumstances in Sinaloa in the last few months, according to a count kept here by journalists.

Two of the victims in Saturday's shootings had criminal records for stealing cars, Leyva said in a rushed news conference Sunday. "Anything is possible," he said.

The dead included two boys, 15 and 16, and two women, 18 and 25, Leyva said.

The shooters escaped, and witnesses said none of those attacked appeared to have returned fire. Authorities said they recovered 95 bullet casings from the scene.

Sinaloa is home to many of Mexico's major drug kingpins, and the cartels hold sway over large parts of the Pacific state. Along with the border state of Chihuahua, it has the highest rate of slayings in the country.

As part of a nationwide military campaign, the government of President Felipe Calderon deployed the Mexican army in Sinaloa in 2007 to fight traffickers and restore law and order. More recently, however, army operations have concentrated on rural regions of the state where vast fields of marijuana have been cultivated for generations.

wilkinson@latimes.com