WASHINGTON — When saboteurs blew up several natural gas pipelines in central Mexico this month, temporarily shutting down production for U.S. automakers and other important manufacturers, a small and shadowy Marxist guerrilla group called the Popular Revolutionary Army reportedly claimed responsibility.
Four explosions in the Bajio, a central region that's both the stronghold of the ruling conservative National Action Party and a big manufacturing zone, disrupted the flow of natural gas between Mexico City and Guadalajara, the country's two biggest cities, and paralyzed pipelines in Veracruz and Guanajuato states.
General Motors and Nissan are said to have lost millions of dollars in production at their plants in the region.
Ordinary Americans should have an interest in learning who is behind the attacks and why. Mexico is the second-largest exporter of crude oil to the United States — more than 1.4 million barrels per day as of April — and if unknown assailants can blow up a natural gas pipeline, they could strike as easily at oil. World oil prices are now above $73 a barrel, and further strikes against Mexican energy infrastructure would add to the price jitters.
Mexico is a dangerously soft target since it has more than 17,000 miles of oil pipelines and 8,235 miles of natural gas pipelines to protect. A McClatchy Newspapers investigation in March demonstrated that Mexico's oil installations can be accessed without authorization.
But as the investigation into the July 5 and July 10 bombings drags on, the mystery only grows.
Among the theories: that the bombings were actually the work of drug cartels striking back at a federal government crackdown, or that the attacks were financed by Venezuela's revolution-minded leftist president, Hugo Chavez, or that they were the work of the radical wing of the leftist Party of the Democratic Revolution (PRD), which narrowly lost last year's presidential election.
Mexico's guerrilla movements historically have been small in scale and generally amount to a political nuisance, so attacks on pipelines are highly unusual.
"This could be an isolated event or it could be the start of a campaign. We just don't know," said Raul Benitez, a professor at Mexico's National Autonomous University who has studied the nation's armed guerrilla movements.
The Mexican government hasn't officially blamed the Popular Revolutionary Army, which is known by its Spanish-language acronym EPR, although major Mexican newspapers reported that the group has claimed responsibility and has demanded the return of two colleagues imprisoned or missing in the southern state of Oaxaca.
The EPR's historical base of operations is hundreds of miles away in the impoverished state of Guerrero, far from the attacks and in a bustling industrial region. Authorities say the bombers used sophisticated European-style plastic explosives, which the EPR has never been known to use.
Marxist rebel groups in Colombia routinely sabotage pipelines, but Mexico has no such similar history. The EPR has been around since the 1960s and isn't known for orchestrated attacks that disrupt industry.
"It's a first time for them," said Pamela Starr, a political risk analyst with Eurasia Group and a longtime follower of the murky world of Mexican politics.
In fact, the only time EPR's members were seen in public was in 1996, when they allowed themselves to be photographed with AK-47 rifles while protesting the murder by police of peasants in the town of Aguas Blancas.
The Marxist EPR has historically raised money by kidnapping. It's believed to be responsible for several crude bombs that detonated in Mexico City last November. Those small attacks came against a political party headquarters, a federal electoral court and a branch bank. The EPR also has attacked rural police stations.
"These were simple attacks that speak to the fact that they didn't have the ability to do these kinds of actions. They clearly have not had access to resources," said Jorge Chabat, a political analyst in Mexico City. "To acquire this sort of bomb requires money, and somebody has to give them that money. That is the question."
If it isn't the EPR, the question then is who is behind the bombings. Venezuela's Chavez has made no secret of his disdain for Mexico's conservative president, Felipe Calderon, who during a controversial campaign used Chavez's image to scare voters away from leftist rival Andres Manuel Lopez Obrador.
But intelligence officials in the United States and Mexico say they have no evidence that Chavez is bankrolling the extreme left in Mexico.
Another view is that Lopez Obrador, the bitter loser in last year's presidential contest, is behind the explosions. The oil workers union he helped lead in Mexico's oil-rich south was known to set wells on fire when pressing demands with the state oil company Petroleos Mexicanos.
But Lopez Obrador's Party of the Democratic Revolution (PRD) has criticized the Mexican government for withholding information that the explosions were caused by sabotage.
Other disaffected groups on the militant left include members of the PRD in southern Mexico, elements of Mexico's petroleum workers union and extremists in Mexico's national teachers union.
The most prominent radical group is the Popular Assembly of the People of Oaxaca, known by its Spanish-language acronym APPO. This leftist social movement was engaged in clashes with security forces last year and confronted police again on Monday.
The EPR's own colorful Web site, complete with links for popular art and revolutionary-themed rock and folk music, is operated out of Brussels, Belgium. The managers of that site confirmed to McClatchy that the account was opened after an e-mail correspondence, not in person.
To read McClatchy's earlier story on Mexico's vulnerable oil facilities, go to: http://www.mcclatchydc.com/staff/kevin_hall/story/15928.html
EPR's Web site: http://www.pdpr-epr.org