OREANDA-NEWS. A blast at Pemex's Pajaritos chemical complex killed 13 and injured 136 people yesterday, following a gas leak at a vinyl chloride production plant in the eastern state of Veracruz.

"We know it was caused by a leak … but we still don't know what caused the leak," Pemex chief executive Jose Antonio Gonz?lez Anaya said in a radio interview this morning.

The death toll could rise, Gonzalez said, since there are still many missing.

Out of the 136 injured, 13 are in critical condition and 48 have been released from the hospital, he said.

The leak occurred at about 4:15pm ET at the Clorados 3 plant, which belongs to Petroqu?mica Mexicana de Vinilo (PMV), a joint venture between Pemex and Mexican petrochemicals conglomerate Mexichem. The plant is part of the Pajaritos complex, near the Coatzacoalcos port, a major oil export hub.

The fire was reported under control about three hours after the accident.

The plant was under maintenance when the explosion happened, meaning the victims were workers at Pemex, Mexichem, but also various contractors, Pemex says.

In October 2015, Mexichem said it would add $70mn in investment to an initial $200mn upgrade at the Parajitos complex to expand vinyl chloride production.

Shipments to and from the Pajaritos complex, a major oil export hub in the eastern state of Veracruz, remain unaffected, a Pemex spokesperson told Argus.

In February, another incident at a PMV plant led to the death of a Pemex worker.