A gasoline storage tank at the refinery burst into flames yesterday, with two workers suffering slight burns and seven others treated for dehydration and exhaustion.
Pemex reported that the internal emergency response plan was implemented as soon as the fire started.
The cause of the explosion is unknown and follows a fire at the facility's coker plant in May and a boiler explosion due to excessive pressure build-up in April. There were no injuries in those incidents.
The company also put out a fire elsewhere in the state of Tamaulipas earlier in the week after someone illegally tapped into a fuel pipeline owned by Pemex.
Ciudad Madero is the smallest of the state-owned company's national refineries.