At least 11 persons were killed and several injured in shootings at two bars in Celaya city of Mexico, the police told the Associated Press on Monday.

Ten out of the eleven deceased persons died on the spot. The eleventh victim was declared dead in a hospital, according to the news agency.

A group of 15 armed men stormed into a hotel at 10 pm on Monday local time and threw petrol bombs, according to witness accounts, reported by BBC. The men then opened fire simultaneously in two nearby bars.

Hand-written signs found at the scene of shooting indicate a rivalry between two drug cartels over gaining control of the Guanajuato state, AP reported. The killers were allegedly from the Santa Rosa de Lima gang, and the letters were accusing the owners of the two bars of supporting Jalisco, a rival cartel

The police confirmed that the messages were left behind, but have not ascertained what they could mean.

José Yépez, the former leader of the Santa Rosa de Lima gang was sentenced to 60 years in prison earlier this year, BBC reported. He was arrested on August 1. The gang operates extortion and fuel theft rackets.