The official death toll in an explosion that struck a state oil plant in Mexico on Wednesday, April 20 has risen to 13, BBC News reports.

The head of Mexico's emergency services, Luis Felipe Puente, said the revised death toll came after emergency services went through the site.

The blast hit a facility owned by Mexico's state oil company, Pemex, in the southern city of Coatzacoalcos.

More than 100 people were injured and hundreds had to leave homes. The cause of the explosion is not yet clear.

Footage showed a large fire and huge plumes of smoke. Several explosions have been reported at Pemex facilities in recent years.

Puente tweeted: "We have examined the affected area and can say that unfortunately so far there are 13 people dead."

The incident occurred at around 15:15 local time (20:15 GMT) on Wednesday. Veracruz state Governor Javier Duarte told a radio station the blast was felt 10km (six miles) away.

The fire was under control by early evening, Pemex said. Residents were told to stay indoors because of the possible toxic nature of the smoke from the blast, but Pemex said the smoke dissipated quickly, lessening any possible toxic effects.

Pemex said the part of the factory hit by the explosion was managed by a sister company, Mexichem.

Associated Press reported that the plant produces vinyl chloride, a dangerous chemical used to make PVC pipes and packaging materials.

Exports of oil from the plant, one of the largest terminals for oil distribution in Mexico, would not be affected, the company added.