Reporting from Mexico City — Armed men opened fire on buses carrying assembly-plant workers near the Texas border early Thursday, killing four people and wounding 15 others in the latest spasm of violence to rattle Mexico.
Authorities in the northern state of Chihuahua said the victims, identified as employees of a U.S. car-upholstery plant called Eagle Ottawa, were riding home about 1 a.m. when three company buses came under fire outside Ciudad Juarez.
Officials said they had not determined a motive. Witnesses said gunmen jumped aboard looking for a male passenger.
"As soon as they located him, they got him down and took him away," Jorge Gonzalez, the state prosecutor in charge of the Ciudad Juarez district, told reporters.
The dead included three women and a man. Two of the wounded remained hospitalized by late afternoon.
The so-called Juarez Valley where the converted school buses were attacked has been racked by fighting between powerful drug cartels. But the more than 330 border factories, or maquiladoras, that dominate Ciudad Juarez and surroundings have been left out of the worst of the recent drug violence.
Nonetheless, the escalating violence has forced factories and other businesses to boost security in Ciudad Juarez, where foreign manufacturers are drawn by a large workforce, mostly female, willing to work for low wages.
Carlos Miranda, president of the Ciudad Juarez Maquiladora Assn., said factory buses have been burned by attackers in extortion attempts.
Ciudad Juarez plants, which assemble car parts, electronic goods, office supplies and other products, were hit hard by the global recession. Although the area boasts 50 more plants than in 2007, the number of employees has fallen by more than a fourth, to 176,000 from 239,000, according to Mexico's census bureau.
Eagle Ottawa, an Auburn Hills, Mich.-based firm with two plants in Ciudad Juarez, makes leather interiors for automobiles. In a statement, the company said it would comment "once we're able to understand what happened."
Thursday's shooting came in a week that has seen several mass slayings in Mexico. A day earlier, shooters attacked a carwash in the Pacific state of Nayarit, killing 15 people. On Sunday night, 13 men died when gunmen attacked a drug-rehabilitation center in Tijuana. On Oct. 23, armed men opened fire at a party in Ciudad Juarez, leaving 14 dead.
Also Thursday, a shooting in Mexico City left six people dead. Authorities said the killings, in a crime-ridden district known as Tepito, followed a dispute that may have centered on a stolen vehicle.
Tepito is a hotbed for stolen and pirated goods and the site of police raids that regularly escalate into violent street clashes.