REYNOSA, Mexico (March 13, 2010)--The border city of Reynosa, Mexico, across from McAllen, has escaped the worst of Mexico’s bloody drug war for years, but now the bodies are piling up and once-busy streets are empty after dark.

The crumbling of an alliance between two Mexican drug gangs has plunged the 200-mile stretch of border into violence.

A U.S. anti-drug official told The Associated Press it is also raising fears of a new front in the drug war.

In Mexican border cities stretching from Matamoros near the Gulf to Nuevo Laredo, gunfire has been heard almost daily.

At least 49 people were killed in drug-related violence in less than six weeks.

Reynosa's main plaza and Calle Hidalgo, a pedestrian shopping street, still bustle during the day, and shoe shiners were doing a brisk business on a recent afternoon, but clothing store manager Manuel Diaz said the streets are deserted by evening, probably because shoppers are scared.

The Pacific coast city of Tijuana and Ciudad Juarez, across from El Paso, have long been wracked by open warfare among rival cartels.

Until recently, border cities to the east had enjoyed relative calm.