Police take positions during a shootout at a prison in Ciudad Juarez [REUTERS]
Seventeen people have been killed in a prison gunfight in Ciudad Juarez, Mexico's most violent city, on a day of events that underscores the fast-moving and violent nature of Mexico's deepening fight against drug gangs and lawlessness.
The deadly prison riot erupted late on Monday, a day before a Washington report was released stating that firearms used in botched US undercover operations were increasingly finding their way into the hands of drug cartels.
Also on Tuesday, the body of a police beat reporter was found in the Gulf coast state of Veracruz, the second reporter from the same newspaper slain in a month.
More than 40,000 people have been killed in drug-related violence since Mexican President Felipe Calderon sent in the army to crush the cartels shortly after taking office in late 2006.
Roughly a quarter of the deaths have been in Ciudad Juarez. The city on the border with Texas has been racked by a brutal turf war between the local Juarez cartel, and the powerful Sinaloa cartel, headed by Mexico's most wanted drug boss, Joaquin "Shorty" Guzman.
Security has also been a serious problem in prisons, which are prone to outbreaks of violence and escapes.
Earlier this month, 59 inmates broke out of prison and a further seven were killed in Nuevo Laredo, a northeastern city also near the Texan border.
A spokesman for the mayor's office in Ciudad Juarez said Monday's gunfight began when an unspecified number of inmates entered two pavilions containing 13 other prisoners. Sixteen men and one woman were killed in the ensuing violence.
"It was first believed to be an escape attempt, but it turns out it was a revenge attack between groups in the prison," said Carlos Gonzalez, spokesman for the Chihuahua state prosecutor's office, on Milenio television.
Some of the deceased bore bullet wounds, and authorities were investigating if the weapons used in the fighting were stolen from prison guards, homemade or smuggled into the jail, he added.
At least 122 firearms from US undercover operation have been found at crime scenes in Mexico or intercepted en route to drug cartels there, the Republican congressional report issued on Tuesday said.
Mexican authorities found AK-47 assault rifles, powerful .50 calibre rifles and other weapons as early as November 2009 that were later linked to the US sting operation to trace weapons crossing the border, the report said.
US authorities set up the undercover operation, dubbed "Operation Fast and Furious," in 2009 to try to track guns bought in Phoenix on behalf of Mexican drug cartels, but many of the weapons were never traced after they left the hands of the initial buyer.
Of the 2,000 weapons sold to the suspected gun traffickers, just over half remain unaccounted for, the report added.
The sting has become an embarrassment for the US government and its Justice Department, rather than a
victory in stemming the illegal flow of weapons to Mexico.