An American mom is dead and her teenage sister is in critical condition after 20 people were killed in a massacre at a cock fight.

Melissa Silva and her sister Arleth Silva, 16, were on vacation in Michoacan, Mexico, and were at the gathering when gunfire rang out, family told ABC7.

Melissa, who is a mother of four, was fatally shot and Arleth was struck multiple times.

Seventeen men and three women were shot dead during the bloody massacre in the Las Tranjas region.

Arleth is currently in critical condition at a hospital in Mexico. She is one of four that were hurt in the shooting.

She was shot once in the lungs, and twice in the legs, a family member claimed on a GoFundMe page.

Prosecutors claimed that the shooters planned the attack and entered the area in a stolen truck owned by a snack food company.

“The snack food company truck arrived, and several armed people in camouflage clothing got out,” a prosecutors’ statement said, according to the outlet.

“At the same moment, a bus that was outside the building was used as a blockade,” apparently to prevent victims from escaping or calling for help, it said.

The incident took place just after 10:30 p.m. on Sunday night as a suspected team of cartel members wearing military uniforms burst into the crowded venue.

Investigators found 15 vehicles, allegedly belonging to the victims. One of which had stickers on with the logo of a criminal gang.

Cops also discovered more than 100 assault rifle bullet shells littered across the ground.

Prosecutors added that drug cartels and other gangs had been fighting in the area.

“There are indications that the attack involved a confrontation between criminal groups,” the federal Public Safety Department said in a statement.

Mexico’s President, Andres Manuel Lopez Obrador, blamed criminal gangs in the area for the killings, vowing that a full investigation would take place.

“It was a massacre of one group by another,” he told a news conference.

On Monday, Mexican army and national guard troops were deployed to capture those responsible.

VIOLENCE CONTINUES TO RISE

Last month, it was revealed that gang violence in Mexico is continuing to rise at an alarming rate amid a bloody new cartel war.

The violence has even spilled over into popular tourist resorts such as Cancun and Playa del Carmen.

In January, two Canadians were murdered by a hitman who had a wristband to get past security at the Hotel Xcaret resort, south of Playa del Carmen.

And in November four Americans were injured in a deadly shootout between rival dealers on a beach next to the five-star Hyatt Ziva Riviera in Cancun.

That came a fortnight weeks after two women — a California travel blogger and a German tourist — were killed in crossfire between rival gangs at a resort bar in Tulum.

Tourism chiefs now fear the bloodshed means the Quintana Roo region will lose its reputation as a safe haven for package holidaymakers and spring breakers.

The governments of the UK, US, Australia, New Zealand and Germany have all issued travel warnings about the resorts.

Experts say it is the visitors themselves who are driving the gang war — as they fuel the rising demand for illicit drugs.

Robert Almonte, who is an expert on Mexican drug cartels, told The Sun that he believes the violence has stemmed from battles being fought between the two main drug cartels operating in the area, the Gulf Cartel and the Jalisco New Generation Cartel.

The notorious Sinaloa Cartel once led by jailed drug kingpin Joaquín “El Chapo” Guzmán is also active at the resorts.

This story originally appeared on The Sun and has been reproduced here with permission.