Morelia, Mexico: A gang brought down a helicopter during a police operation in Mexico’s troubled western state of Michoacan on Tuesday, killing the pilot and three officers, the governor said.

The aircraft was backing an operation to arrest leaders of criminal groups when the ‘official helicopter was downed’ in an area with rough terrain, Governor Silvano Aureoles wrote on Twitter.

Another officer was injured in the crash.

Aureoles did not say how the helicopter was shot down in the region of Apatzingan, a city located in Tierra Caliente (Hot Land), a region that has been beset by drug violence and vigilante justice for years.

‘In accordance to the responsibility to protect citizens, the state and federation won’t give up in the frontal fight against crime,’ the governor wrote.

It is the second time since 2015 that a gang downs a helicopter in Mexico. Last year, the Jalisco New Generation drug cartel in neighbouring Jalisco state used a rocket launcher to hit a military helicopter, killing seven soldiers and policewoman aboard.

In Michoacan, the pseudo-religious Knights Templar drug cartel held sway in Tierra Caliente until lime growers formed vigilante forces in 2013 to fight back against the gang.

The cartel was weakened as authorities arrested or killed its top leaders, but smaller criminal groups have since emerged.

Homicides are on the rise in the state, with 678 murders in the first seven months of the year compared to 777 in 2015.

Anti-tank missile

Tuesday’s clash followed a series of shootouts over the weekend that left no casualties but led to the seizure of weapons that included the discovery of an anti-tank missile, according to a report by the state prosecutor’s office.

Federal forces exchanged fire with armed civilians who eventually escaped on Friday in the port of Lazaro Cardenas.

On Saturday, agents were attacked in the town of La Concepcion but the gunmen fled, leaving behind a vehicle that contained 8.3 kilograms (18.3 pounds) of methamphetamines.

It was on Sunday in the town of Mugica, in Tierra Caliente, that the missile was found after soldiers clashed with gunmen, who fled the scene. The suspects also left behind five pickup trucks and two rifles.

Michoacan state government secretary general Adrian Lopez Solis told AFP on Monday that ‘incidents of insecurity still persist’ in the region.

Michoacan has bedevilled the Mexican government for years. It was there that then president Felipe Calderon deployed troops for the first time against drug cartels after he took office in December 2006.