By Raul Cortes and Adriana Barrera
MEXICO CITY, March 26 (Reuters) - An oil spill in the Gulf of Mexico was caused by both natural causes and a petroleum tanker that authorities are still trying to identify, Mexican officials said on Thursday.
Raymundo Morales, the head of the Mexican navy, said satellite images showed a slick off the coast, and noted that any one of 13 vessels that had passed through the area could potentially be responsible for the discharge.
Four of the vessels are still sailing in Mexican waters and were being inspected by the navy, Morales said. Mexico has requested international cooperation to inspect the remaining nine, which are now in international waters.
Morales added that two spots of natural submarine oil seepage have also contributed to petroleum products being washed up on Mexican shores.
One source of the submarine leak from seabed is ongoing, Morales said, and is believed to be the greatest contributor. At the other spot, seepage has been intermittent and is currently contained.
"We need to assess what is happening, whether the natural seepage has increased or if there is a structural failure on one of the platforms," Morales said.
In coordination with Mexico's state energy company Pemex, authorities are deploying marine barriers to prevent the spill from further damaging wildlife and beaches in the affected areas, Morales said.
Pemex is also conducting underwater checks to rule out structural failure of oil rigs, Morales said.
The spill has affected marine life and stained beaches in the southern states of Tabasco, Veracruz and Tamaulipas, although environment minister Alicia Barcena said at the press conference that the damage is not "severe."
The issue appeared around the same time as an incident March 17 in which five people died outside Mexico's Olmeca oil refinery after "oily waters" around the perimeter caught fire.
(Reporting by Raul Cortes and Adriana Barrera, Writing by Natalia Siniawski and Iñigo Alexander, Editing by Daina Beth Solomon)
