A huge oil plant explosion in Veracruz state in southeastern Mexico has killed three people and injured at least 30 others. According to reports, hundreds of people were also evacuated after the blast struck a facility owned by state-run oil company Petroleos Mexicanos, or Pemex in the industrial port city of Coatzacoalcos.

"We regret to inform that at the moment the current number of injured from the accident ... is 30," the company said in a tweet. The figure was disputed by Veracruz's head of public security, Arturo Bermudez, who told local television that 40 people had been wounded. Three people were originally reported to have been injured, but the number was later raised.

Images of the blast were broadcast on Mexican television and showed thick black smoke billowing into the air. Veracruz governor Javier Duarte called it a "strong explosion" and told reporters that he was informed three people had been killed in the incident, according to a Reuters report.

While the cause of the blast is not yet clear, it comes just weeks after three workers were killed and seven others were injured in a fire on a Pemex oil-processing platform in the Gulf of Mexico, raising questions about safety. The incident occurred at 3.30pm local time (8.30pm GMT).

The BBC reported that the blast took place in a part of the plant managed by Pemex's sister company, Mexichem. Pemex dominated Mexico's oil and gas sector until 2014, when energy was opened up by reforms. Recently, the company has been hit hard by the steep decline in oil prices, forcing it to implement heavy cost-cutting measures.

Pemex has been dogged by a series of high-profile accidents in recent years. In 2013 the company's headquarters in the capital, Mexico City, was rocked by a large gas blast, killing 37 people. A year earlier, 33 people were killed at a gas plant in the northern state of Tamaulipas when it was hit by an explosion followed by a fire.