Related articles:

Terror in Mexico Attacks on Mexican gas pipeline force factories, businesses to temporarily shut down

Other articles by Pablo Bachelet:

Calderón set to court S. American nations, downplay emigration Latin America no longer smiling on U.S. aid Tucson a hub for Mexicans' drug trade

Other articles by Kevin Hall:

Calderón set to court S. American nations, downplay emigration New rules will track status of entrants Vote to determine future of nation too close to call Next Federal Reserve chairman Bush urges Americans to cut back on car trips

Trades/Construction
.
Welders, Fabricators for structural steel Office and Clerical
Dr. Wayne Goodner, DDS
Front Office PT Sales and Marketing
Everready Glass
Glass Sales Driver/Transportation
DRIVERS Health Care
Neurological Associates of Tucson
Operations Manager Technical
INSTALLER Sales and Marketing
sales

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, or 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.

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.

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.

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.

"These were simple attacks that speak to the fact that they didn't have the ability to do these kinds of actions," said Jorge Chabat, a political analyst in Mexico City.

"They clearly have not had access to resources. 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 Calderón, who during a controversial campaign used Chavez's image to scare voters away from leftist rival Andrés Manuel López 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 López Obrador, the bitter loser in last year's presidential contest, is behind the explosions. The oil workers union he helped lead in Mexico's south was known to set wells on fire when pressing demands with the state oil company Petroleos Mexicanos.

But López Obrador's Party of the Democratic Revolution, or 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 the petroleum workers union and extremists in the teachers union.