This car exploded in front of the offices of the Televisa network in Ciudad Victoria, Tamaulipas. Another went off in front of transit-police offices.

REYNOSA, Mexico - A car explodes outside a police station, another outside a television station. A gang is suspected of massacring 72 migrants. A prosecutor investigating those deaths suddenly disappears.

Mexico's drug cartels seem to be adopting the tactics of war zones half a world away.

The violence appears to have contributed to fewer migrants crossing the border into the U.S., officials say, as they have to traverse some of Mexico's most dangerous territory to get to Texas. Mexican officials, meanwhile, warn that there likely will be more in the coming months.

"Violence will persist and even intensify," President Felipe Calderón said at a forum on security where he vowed he would not back down.

If authorities confirm the explosions were car bombs, it would mean a total of four such explosives have been used this year in Mexico - a new and frightening tactic that officials say the cartels are using in the escalating drug war.

No drug gangs claimed responsibility for Friday's violence in the northern state of Tamaulipas. A survivor of the massacre, however, said the killers identified themselves as Zetas, a group of former Mexican army special-forces soldiers who are now a lethal drug gang that has taken to extorting migrants.

Kidnappings and attacks on government security patrols are rampant in the highways surrounding San Fernando, where the bodies of the 72 Central and South American migrants were discovered on a ranch Tuesday, bound, blindfolded and slumped against a wall.

The car blasts happened less than 45 minutes apart in Ciudad Victoria, the Tamaulipas capital, the Attorney General's Office said. The first car exploded in front of the offices of the Televisa network, the second in front of transit-police offices. There were no injuries.

Investigators have identified 31 of the migrants, whose remains were taken to Reynosa, a city across the border from McAllen, Texas. Those identified include 14 Hondurans, 12 Salvadorans, four Guatemalans and one Brazilian.

The prosecutor, Roberto Jaime Suarez, disappeared Wednesday in San Fernando, where the bodies of the migrants were found, the state Attorney General's Office said. A transit police officer in the town is also missing.