Traffic resumed between the twin cities of Eagle Pass, Texas, and Piedras Negras, Mexico, after both International Bridges temporarily shut down last night.

Tony Castaneda said it was the first time he can recall in his 18 years as Eagle Pass police chief that "gunfire between the military and organized crime figures" shut down the bridges.

Castaneda said two major confrontations erupted after a military convoy was attacked by those believed to be enforcers for the Zetas cartel.

He said that led to roadblocks by gang members to keep out reinforcements as running gun battles paralyzed much of Piedras Negras.

Castaneda said the gunfire and grenade explosions could be heard in Eagle Pass.

He said several of his officers who are ex-military who recognized the sound of the 0.50-caliber guns used in response.

"When something of this magnitude occurs, it creates fear," he said -- on both sides of the border.