MEXICO CITY - Dark days of violence have returned to Mexico's northeastern state of Tamaulipas, prompting authorities to deploy more soldiers after nearly 80 people died in drug cartel gunfights in one month.
A spate of shootings in broad daylight and high-speed chases through city streets have turned Tamaulipas into a new security challenge for President Enrique Pena Nieto.
On Wednesday authorities announced the arrest of 10 state police officers for alleged links with organised crime. Press reports said they may be tied to the murder of a police chief.
Until now, the western state of Michoacan had been the centre of attention after the federal government deployed thousands of troops to end battles between vigilantes and the cult-like Knights Templar drug cartel.
But a new bout of violence has put the spotlight again on Tamaulipas, a state bordering the United States that has endured some of the worst carnage in Mexico's drug war.
The shootings have broken a rare lull in a state accustomed to battles between the Zetas and Gulf cartels, former allies that turned on each other in recent years.
Many of the 80,000 victims of Mexico's drug war have died along the country's northern states since 2006, due to their prime locations as lucrative drug trafficking routes to the United States.
Officials say the latest spate of violence is the result of crackdowns on gangs and an internal feud within the Gulf cartel following the arrests of top capos.
At least 77 people have been killed since April 5, according to official figures, even as the federal government says killings have fallen nationwide since Pena Nieto took office in December 2012.