MEXICO CITY -Federal crime investigators began their probe Monday of what caused a massive oil pipeline explosion that killed 28 people and laid waste to parts of a central Mexican city.
Valentin Meneses, interior secretary for the state of Puebla, where San Martin Texmelucan is located, said 32 homes were completely destroyed and 83 partially damaged by the blast.
"A commission has been named that together with Pemex (Petroleos Mexicanos, the state oil company) is investigating what happened," Meneses said.
The scene of the disaster has been closed off and is being patrolled by police, Meneses added. Cleanup experts are also making sure there is no combustible material remaining in drains, which could threaten a new explosion.
Sunday's blast in San Martin Texmelucan, about 55 miles (90 kilometers) east of Mexico City, left metal and pavement twisted and in some cases burned to ash in the intense heat.
Thirteen of the dead were children, and at least 52 people were injured. Scores of displaced residents were still in shelters Monday, though officials have not given an exact figure.
Authorities say thieves attempting to siphon oil caused a leak in the pipeline, sending black crude gushing into a street and flowing into a nearby river. It is not known what caused the oil to ignite.
Investigators found a hole in the pipeline and equipment for extracting crude, according to Laura Gurza, chief of the federal Civil Protection emergency response agency.
Authorities including President Felipe Calderon have promised to stop at nothing to bring whoever is responsible to justice. There have been no arrests so far, however.
Pemex has struggled with chronic theft, losing as much as 10 percent of all of its product. Criminals tap remote pipelines, sometimes building pipelines of their own, to siphon off hundreds of millions of dollars' worth of oil each year, Pemex has said.