Mexico City (AFP) - An explosion and a fire erupted on an offshore oil platform operated by Mexico's Pemex on Wednesday, killing at least four workers, injuring 16 and forcing 300 to be evacuated.Eight firefighting vessels with water cannons were deployed to battle the blaze as smoke billowed skyward at the Abkatun A-Permanente platform on the Gulf of Mexico's Campeche Sound.The blast took place at 3:40 am in the dehydration and pump area of the platform, located off the coast of eastern Campeche state, the ASEA energy safety agency said in a statement."The fire is under control but has not been extinguished," a Pemex spokesman told AFP.Pemex issued a statement saying that the fire "did not cause a spill into the sea" but that an oil leak occurred and was being contained by specialized ships.The company said 16 people were hospitalized, including two in serious condition. A total of 45 people received medical attention, but most were released with minor injuries.Some 300 workers were taken to other platforms in the area, while the injured were transported to Pemex's general hospital in Ciudad de Carmen.AFP obtained a video taken from a boat showing huge flames and smoke engulfing much of the platform in the middle of the night.Pemex director Emilio Lozoya said there will be little impact to production as the fire occurred on an oil processing rig, not a producing facility, and that the crude would be shipped to other facilities.- Investigation ordered -Pemex said one of the dead was a company employee, while another one worked for Cotemar, a contractor.