Mexican police have arrested three men over a bloody gun attack on a drug rehabilitation center that left 27 people dead, the local prosecutor's office said Sunday.
Gunmen burst into the center in the city of Irapuato in the central Guanajuato state on Wednesday, forcing victims "onto the ground and shot them", authorities said.
The suspects were captured in a swoop by special forces, the prosecutor's office said on Twitter, calling the incident a "heinous crime."
Mexico's President Andres Manuel Lopez Obrador has condemned the attack -- the deadliest of its kind this year in the country. The original death toll was 24, but three of those who were injured have since died.
The president called on the Guanajuato government, which is in opposition hands, to investigate whether the violence could be partly due to "conspiracy" between local authorities and criminal gangs.
According to local media, the attack was part of an ongoing battle between rival cartels.
The presence of large-scale energy infrastructure in Guanajuato has attracted gangs such as the Santa Rosa de Lima cartel, which deals in stolen fuel and is battling the powerful Jalisco New Generation cartel for control of the lucrative trade.
On June 21, authorities said they had captured 26 suspected members of the Santa Rosa de Lima cartel, which responded by setting up blockades of burning vehicles in three cities.
Several days earlier six members of one family, including a minor, had been murdered in the city of Celaya, one of those where the gang set up roadblocks.
Wednesday's attack was the second-most lethal assault since Lopez Obrador came to power in December 2018, after 28 people were killed at a bar in the eastern state of Veracruz last August.
Since December 2006 when the then-government launched a military operation against drug trafficking gangs, more than 290,000 people have been murdered, according to official figures.