Statistics published Tuesday by the Interior Department said 2,186 people were murdered last month. The previous monthly high was 2,131 in May 2011, according to a review of publicly available records that date back to 1997.
During the first five months of 2017, there were 9,916 killings nationwide — an increase of about 30 per cent over the 7,638 slain during the same period last year.
"Pretty grim. Not shocking, because we've seen this for months," Mexican security analyst Alejandro Hope said. "But, yeah, it's really grim."
Mexico launched a militarized offensive over a decade ago to combat drug cartels that plague parts of the country. Homicides fell somewhat after peaking in 2011 but have risen again.
At the state level, Baja California Sur saw the biggest jump in the first five months of 2017. After registering 36 killings during the same period in 2016, that spiked by 369 per cent to 169 this year.
There were also significant increases in Veracruz (93 per cent), Quintana Roo (89 per cent) and Sinaloa (76 per cent).
On Wednesday, Veracruz Gov. Miguel Angel Yunes said at a news conference that seven bags containing two dismembered bodies had been left outside the personal office of the state security chief Tuesday night. Armed men had also attacked three workers hanging a billboard with photographs and a reward offered for area criminal suspects.
Hope said the violence is being driven in part by "the weakening of the Sinaloa drug cartel" — whose top boss, Joaquin "El Chapo" Guzman, was extradited to face drug charges in the United States earlier this year. Hope also noted "the parallel rise of the Jalisco (New Generation) cartel."
In Baja California Sur in particular, Hope said, a Sinaloa faction is battling for control both against rivals within the cartel and externally against Jalisco. Hope also cited increased heroin trafficking, difficulties implementing a new criminal justice system and insufficient federal police response to the crime surge.
Total homicides for the January-May period declined from 2016 in just four states — Campeche, Coahuila, Mexico State and Nuevo Leon — and nowhere did the drop exceed 6 per cent.
Associated Press writer Lev Garcia in Xalapa contributed to this report.
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