MEXICO CITY — Mexican authorities on Thursday announced the arrest of a suspected drug-gang leader who allegedly directed the fatal car-bomb attack in Ciudad Juarez last summer that stoked fears of a dangerous escalation in the drug war.

Fernando Contreras Meraz, identified as a regional boss of an armed gang known as La Linea, was arrested Wednesday in the northern city of Chihuahua with 13 other suspects, federal police officials said.

Contreras is accused of overseeing the July 15 blast that killed four people, including a police officer, on a busy Juarez street. Contreras detonated the bomb by cell phone, police said.

The attack, which officials said targeted federal police, was the first successful use of a car bomb here since President Felipe Calderon declared war on drug cartels four years ago.

The incident stirred worry that Mexico might face a new stage of violence like that seen in Colombia during the worst of its drug-related carnage. In subsequent weeks, three cars exploded in the northern state of Tamaulipas, though no one was hurt.

A top federal police official, Luis Cardenas Palomino, said a series of arrests have left La Linea near collapse. The group, whose ranks have included numerous Juarez police officers, works closely with the so-called Juarez cartel.

In the July bombing, attackers sought to lure authorities by dumping an injured man dressed as a municipal police officer near the explosives-laden car. A doctor who approached was among those killed when nearly 20 pounds of explosives detonated.

In other developments, U.S. officials were investigating the fatal shooting in Juarez of a 22-year-old member of the Texas National Guard. Jose Gil Hernandez Ramirez, identified as a student and part-time Guardsman, and a second man were slain Wednesday.

Guard officials said they didn’t know what Hernandez, who lived on the U.S. side of the border in El Paso, was doing in Mexico.