Anxious search for missing after deadly Mexico blast

Anguished relatives nervously awaited news of their loved ones Thursday outside a Mexican petrochemical plant where an explosion killed at least 13 people and sent toxic smoke billowing into the air.

Starting at dawn, family members flocked to a military cordon set up around the plant after Wednesday's explosion, which blew out the windows of nearby stores and homes and triggered panic among locals still traumatized by a deadly blast at the same facility 25 years ago.

About 300 people had gathered by midday outside the plant in Coatzacoalcos, in the eastern state of Veracruz, some weeping loudly, some scuffling with soldiers.

"We want them to cut to the chase and give us (our relatives). If they don't let us through, we'll force our way in," said Guadalupe Torres, whose 21-year-old brother Fernando was working a temporary job at the plant and was among the 18 officially missing.

Many outside the plant said they feared the real missing number was far higher.

A worker who survived the explosion told journalists some 300 employees were on site when the blast occurred.

"I was out back when the first explosion came. We saw the windows collapse, the iron bars crumple, because (the facilities) are extremely old," he said.

"When the second explosion happened, I saw bodies fly off the scaffolding."

Pemex chief executive Jose Antonio Gonzalez Anaya said the explosion was caused by a gas leak.

The plant, known as  Petroquimica Mexicana de Vinilo (PMV), "uses flammable materials like chlorine and ethanol but we do not know the cause of the leak," he told Televisa television.

Pemex co-owns the plant with a private company, Mexichem, which operates the facility.

An employee of a contractor at the site, Jose Antonio Galicia, said the plant had been registering leaks for weeks.

- Schools closed -The release of toxic columns of black smoke sowed panic in the area as officials initially warned residents to stay indoors.

But Mexican authorities and Pemex officials later said the cloud posed no threat to the population.

Around 2,000 evacuated residents returned home Thursday, and life in the town was returning to normal as the dissipating cloud drifted into the distance -- though schools remained closed.

President Enrique Pena Nieto sent his condolences to victims' families and announced he would visit the site.

The death toll could rise further as 136 people were injured, 13 of them critically.

Soldiers eventually began allowing small groups of family members through the security cordon to ask about their relatives' fate.

- 'Time bomb' -Some residents were still in shock.

"I left my house running. I thought the whole city was going to catch fire," said Marcela Andrade Moreno, whose windows were blown out.

Other terrified locals feared a repeat of the 1991 explosion at the same facility. The death toll from that incident officially stands at six, although local media insist the number is much higher.

"We live in a time bomb," said Abelardo Garduza, a merchant from the village of Allende, located a few kilometers from the plant.

Pemex has had to deal with several deadly accidents at its land-based and offshore facilities in recent years.

Even its headquarters –- a skyscraper in the heart of Mexico City –- was hit in January 2013 by a blast caused by a gas buildup, killing 37 people.

Accidents have hit several oil rigs in the Gulf of Mexico, while fires have erupted in pipelines after fuel thieves punctured them.

In February, two people were killed and at least seven injured in a blaze at a Pemex oil platform off the coast of Campeche, also in the southeast.

Pemex provides one-fifth of the Mexican government's revenue but has posted huge losses amid crumbling production and oil prices.

The government has implemented a sweeping reform of the energy sector which opens it to foreign investors for the first time in decades and partly aims to help modernize aging infrastructure. —Agence France-Presse