Twenty four people have died after a leak caused an explosion at a petrochemical plant on Mexico's southern Gulf coast, and the death toll could still rise, Mexican oil giant Pemex said on Thursday.
Pemex raised the toll late Thursday from the 13 fatalities previously known and announced eight workers remained missing. It also said 19 people remained hospitalised, with 13 of them in serious condition.
In a statement, the company said 12 of the bodies had been identified and eight of them delivered to family members.
Earlier in the day, President Enrique Pena Nieto visited the facility in the industrial port city of Coatzacoalcos and met with relatives desperate for word on the fate of loved ones still unaccounted for.
"I understand the anxiety, the worry, the anguish you are going through," Pena Nieto said, assuring them that both Pemex and the Mexichem Company, which co-operated the plant, would fulfil their responsibilities and compensate those hurt by the accident.
A worker who survived the explosion told journalists that 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."
The sharp odour of ammonia filled the air and the plants' turbines still streamed gray smoke on Thursday afternoon, where local and municipal police, as well as marines, blocked the entrance to the facility.
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.
Around 30 families, some weeping loudly, some scuffling with soldiers, gathered at a plant entrance road, where a sharp chemical smell still hung in the air about 2 kilometres (a mile) from where the explosion occurred Wednesday afternoon.
A group of relatives unsuccessfully tried to force their way into the installation, shouted at marines and soldiers who were called in to guard the facility, and they threw rocks at a white government SUV when it arrived at the scene.
Some volunteers brought food and drink to the families. After a while authorities commenced taking people inside in small groups to see a list of those confirmed dead. Some left crying after seeing their loved ones' names.
Jose Antonio Gonzalez Anaya, Pemex's director, told Radio Formula that the explosion was caused by a leak of an as-yet unknown origin.
Rosa Villalobos travelled about four hours by bus from the city of Veracruz looking for her son at Coatzacoalcos hospitals, Luis Alfonso Ruiz Villalobos, a 25-year-old worker at the plant. When she couldn't find him she showed up at the plant entrance.
"What I want is for justice to be done in my son's case, for there to be no impunity," Villalobos said. "I'm going to stay here. Even though I have no money, even though I have nothing to eat, I'm staying put."
The incident took place at Petroquimica Mexicana de Vinilo, or PMV, a vinyl petrochemical plant that is a joint venture between Pemex's petrochemical unit and Mexican plastic pipe maker Mexichem.
Pemex co-owns the plant with a private company, Mexichem, which operates the facility.
Antonio Mariche, who accompanied the Villalobos family in search of Luis Alfonso, vowed that the families would demand a full account of what happened.
"To the president, to the state governor, to the head of Pemex, we will not allow any more cover-ups like have happened with previous accidents," Mariche said.
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.
The incident occurred just weeks after three workers were killed and at least seven injured when a fire broke out on a Pemex oil-processing platform in the Gulf of Mexico.
Pemex provides one-fifth of the Mexican government's revenue but has posted huge losses amid crumbling production and dropping oil prices.
The government has implemented a large-scale reform of the energy sector which opens it to foreign investors for the first time in decades and partly aims to help modernise aging infrastructure.