Morelia, Mexico: A police helicopter crashed on Tuesday during an operation to capture suspected gang leaders in western Mexico, and authorities were investigating whether gunmen shot it down, killing three officers and the pilot.

Silvano Aureoles, governor of the troubled western state of Michoacan, wrote on Twitter that the helicopter “was downed” during the operation in an area of rough terrain.

But hours later, he told the Televisa network that he “can’t confirm that it was downed” and that authorities were investigating the cause of the crash.

Officials are hoping to speak with an officer who survived the crash but was in intensive care.

The incident took place in Michoacan’s Tierra Caliente (Hot Land), a region that has endured years of drug violence and vigilante justice.

If confirmed, it would be the second time that a gang has downed a helicopter since 2015. 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 a policewoman aboard.

But regardless of how the helicopter crashed on Tuesday, it happened amid a resurgence of violence in Michoacan, a historic flashpoint in Mexico’s war on drugs.

In a press conference, Aureoles said the helicopter went down during an operation to capture leaders of an unidentified criminal group who had tried to abduct a farmer in La Huacana.

“Be certain that we will free Michoacan of the scourge of impunity and crime,” Aureoles said.

Aureoles said authorities have conducted operations to capture gang leaders in Tierra Caliente and Sierra Costa that, since August 30, led to a dozen arrests and the seizure of several weapons, including two rocket launchers.

The pseudo-religious Knights Templar drug cartel terrorised 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.

The vigilantes have been ordered to disband but some of the militia’s members have been implicated in crimes.

Homicides are on the rise in the state, with 678 murders in the first seven months of the year compared to 777 in 2015, according to federal government figures. At least 150 people were killed in July alone, a two-fold increase from the same month last year.

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.

President Enrique Pena Nieto has maintained his predecessor’s militarised campaign against the gangs, including in Michoacan.

Murders fell nationwide in the first two years of Pena Nieto’s presidency but they rose again last year. There were 11,257 homicides in the first seven months of this year, up from 9,613 over the same period in 2015.

Michoacan is back in the spotlight this year.

In July, 10 burned bodies were found in burnt vehicle on a dirt road. The mayor of the town of Alvaro Obregon and four local police officers were detained in connection with the crime.

Tuesday’s helicopter crash 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.

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

Michoacan’s cardinal and Roman Catholic bishops have issued a letter denouncing the rise in violence and the persistent extortion bids by criminals against citizens.