MEXICO CITY -- Ten people were murdered in Rosario, a town in the northwestern Mexican state of Sinaloa, in an incident apparently linked to organized crime, officials told Efe.

The killings occurred Wednesday night, according to the officials, who did not provide further details.

Nine people were pronounced dead at the shooting scene under a bridge and the tenth person died while being transported to a hospital.

"We don't know if it was a clash or an execution (carried out by gunmen working for drug cartels)," one of the officials said.

Officials at Rosario city hall confirmed there had been a shooting in the town, but they said only nine people were killed.

Journalists told EFe that AK-47 assault rifles were found at the crime scene, indicating there may have been a shootout between rival groups.

Sinaloa is the birthplace of some of the most notorious drug traffickers in Mexico and the base of Joaquin "El Chapo" (Shorty) Guzman's cartel, which has been fighting a bloody war across Mexico against the rival Gulf cartel.

Mexico has been plagued in recent years by drug-related violence, with powerful cartels battling each other and the security forces, as rival gangs vie for control of lucrative smuggling and distribution routes into the United States.

Armed groups linked to Mexico's drug cartels murdered around 2,700 people in 2007 and 1,500 in 2006, with the death toll this year at more than 5,300, according to press tallies.

Experts say that Mexico's most powerful drug trafficking organizations are the Tijuana cartel, the Gulf cartel and the Sinaloa cartel. Two other large drug trafficking organizations, the Juarez and Milenio cartels, also operate in the country.

Tackling the problem of drug-related violence, according to experts, is a major challenge both because of Mexico's notoriously corrupt security forces and because honest police officers are fearful of taking on the heavily armed drug mobs.

Since taking office in December 2006, President Felipe Calderon has deployed more than 30,000 soldiers and federal police to nearly a dozen of Mexico's 31 states in a bid to stem the wave of violence unleashed by drug traffickers.

The anti-drug operation, however, has failed to put a dent in the violence due, according to experts, to drug cartels' ability to buy off the police and even high-ranking prosecutors.

The Attorney General's Office recently began investigating its own staff, particularly the SIEDO organized crime unit's members and the Federal Investigations Agency, Mexico's equivalent of the FBI.

As part of the probe, begun after a protected informant revealed links between drug cartel kingpins and police, a dozen high-ranking officials, including erstwhile drug czar Noe Ramirez, have been arrested.

The initial investigation concluded that Ramirez received $500,000 a month for sharing intelligence with drug lords.