Mexico registered more than 2,000 murders in May, a record high for any month since 1997, underlining the country's struggles to deal with the trade in narcotics.
There were 2,186 murder investigations in May, according to the latest government statistics released on Wednesday, surpassing the previous monthly high of 2,131 in May 2011.
Some cases may include multiple homicides, and the number of murder victims reported in May was 2,452, the highest for any month in a separate series of data that only goes back to 2014.
The deadliest state was Guerrero, in the south, a hotspot in Mexico's war on drugs where 216 people were killed.
Murder investigations in the first five months of the year totalled 9,916 cases, up nearly 30 percent from the same period in 2016.
The violence surrounding the multibillion-dollar drugs trade has contributed to a slump in the popularity of President Enrique Pena Nieto, and could undermine support for his Institutional Revolutionary Party in next year's presidential race.
In the western state of Sinaloa, where rival factions have been battling for control of the Sinaloa drug cartel since its kingpin, Joaquin "El Chapo" Guzman, was extradited to the US in January, 154 people were killed, the highest number in six years.
Since Mexico first sent the military to fight drug trafficking in 2006, a wave of bloodshed has left more than 200,000 people dead or missing, as rival cartels wage war on each other and the army.
Discoveries of bodies tossed by the roadside, strung up on bridges as warnings to rival drug gangs, or buried in mass graves have become regular events in Mexico.
The capture or killing of major drug bosses during the past decade led to an increase in the number of gangs fighting each other over turf and battling government forces.
According to statistics from the UN Office on Drugs and Crime, Mexico's murder rate in 2015 was 16.35 people per 100,000, higher than the US rate of 4.88 but much lower than in many countries in Central America and the Caribbean.
In an investigative piece for The Nation, Dawn Paley details the "spectacular violence" that has accompanied the drug war project.
"In 2014, Mexico ranked as the country with the third-most civilians killed in internal conflict, after Syria and Iraq. Bodies have been buried, burned, displayed in public places, hung from bridges and overpasses or beheaded and left at city hall."
A report at The Intercept last year noted that in Mexico "98.3 percent of crimes [went] unpunished in 2013, according to Mexican government statistics".