Gunmen have stormed a drug rehabilitation centre in central Mexico, killing 24 people.
At least seven others were injured including three seriously in the attack on Wednesday, according to police.
It is the second attack at a rehab facility in Irapuato, Guanajuato, within a month, and one of the mostly deadly massacres this year.
The motive is unknown but gangs often target clinics where they believe members of rival factions are hiding.
The latest rehab centre to be hit was not officially registered, according to authorities.
The state has hundreds of unofficial treatment centres. The prior attack – at a nearby centre called Starting a New Life – killed 10 people.
Police told local media that, in the latest ambush, several gunmen jumped out of a truck and rushed into the building, where they forced those present to drop to the floor before shooting them.
Witnesses said relatives rushed to the scene and some women – believed to have sons being treated inside – collapsed as the news broke.
President Andres Manuel Lopez Obrador said it was a “very serious situation”.
He called on the Guanajuato government, which is controlled by the opposition, to probe whether the attack could be partly down to a “conspiracy” between local officials and criminal gangs.
Guanajuato’s Attorney General Carlos Zamarripa called it a “cowardly” attack.
A turf war has erupted in Guanajuato, where the local Santa Rosa de Lima gang vies with the brutal Jalisco New Generation Cartel, which has become one of the country’s most dominant organised crime groups.
It is not yet known if either of the groups was involved in most recent attack.
“We have no information on those responsible. There is no data regarding the vehicles or the people,” police told local media in the immediate aftermath.
However, State Governor Diego Sinhue Rodríguez Vallejo said gangs appeared to have been involved.
“I deeply regret and condemn the events in Irapuato this afternoon,” he wrote on Twitter. “The violence generated by organised crime not only takes the lives of the young, but it takes the peace from families in Guanajuato.”
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The state now has the highest number of homicides in the country, according to the National Public Security System (SNSP).
President Andrés Manuel López Obrador, who came into power at the end of 2018, vowed to crack down on the gang violence. However, the national murder rate reached an all-time high in 2019 and this year has brought some high-profile attacks.
Last week, an assassination attempt was made on a Mexico City police chief.
Omar García Harfuch survived after his car was ambushed, but three others – two bodyguards and one passer-by – died in the gunfire.
A federal judge, Uriel Villegas Ortiz, and his wife, Verónica Barajas, were murdered in June.
Both attacks are believed to be linked to the Jalisco New Generation Cartel, but this has not been confirmed as investigations are ongoing.