MEXICO CITY (AP) — Nine people are dead, including four women, after gunmen burst into a bar and opened fire in the violence-wracked Mexican state of Guanajuato, authorities said Thursday.

It was at least the third such bar massacre in as many months in Guanajuato, where a local gang is fighting a turf war with the Jalisco cartel. The common denominator in the attacks is that the assailants have simply tried to kill everyone in the bars, including waitresses.

In the attack Wednesday night in the town of Apaseo el Alto, the attackers left hand-written posters on the blood-covered floor of the bar. The messages were signed by the Santa Rosa de Lima gang, whose now-imprisoned leader is known as the “Marro,” or Sledgehammer.

The messages appeared to accuse the bars’ owners of supporting the rival Jalisco cartel.

Photos from the scene showed the bodies of several mini-skirted waitresses slumped in pools of blood at the bar.

The municipal government of Apaseo el Alto said that two other women were wounded in the attack but are in stable condition.

In October, a dozen people, six of them women, were killed in an attack on a bar in another Guanajuato city. A similar attack on a bar in another town left 10 dead in September.

Guanajuato-based security analyst David Saucedo said the attacks were targeted against specific bars — whose owners may have refused to pay protection money or sold drugs from rival gangs — but were indiscriminate once the targets were selected.

“Some of the attacks have been carried out to kill drug dealers, lookouts or cartel members who were having a night out at the bars,” said Saucedo. “But they become massacres because they kill waitresses and customers, as well.”

There are signs that the conflict in Guanajuato, Mexico’s most violent state, has become a proxy battle between Mexico’s two most powerful drug cartels.

The Sinaloa cartel now appears to be backing the Santa Rosa de Lima gang in its fight against Jalisco.