The Captain of a Panamanian-flagged oil tanker has been  convicted of causing an oil spill  that became an ecological disaster off the island of Mauritius

The captain and first officer of an oil tanker that struck a coral reef in Mauritius, causing the archipelago's worst environmental disaster in the Indian Ocean, were convicted of endangering navigation.

The MV Wakashio, a Panamanian-flagged Japanese freighter, crashed on July 20 and spilled more than 1,000 tons of fuel into the pristine waters of Mauritius, covering mangroves, corals and other sensitive ecosystems.

Captain Sunil Kumar Nandeshwar , convicted Tuesday in a court in the capital Port Louis, admitted to drinking during a party on board.

He and First Officer Hitihanillage Subhoda Janendra Tilakaratna were found guilty of "endangering safe boating" and are due to be sentenced on December 27.

The MV Wakashio was moving from Singapore to Brazil with 3,800 tonnes of oil and 200 tonnes of diesel when it struck the reef off the southeast coast of Mauritius.

"There was a birthday party on board and I consumed alcohol moderately," admitted the captain, who had issued instructions to approach the waters of Mauritius and post a telephone signal that would allow the crew to contact their families.

More than 1,000 tons of oil leaked into the waters teeming with marine life through a crack in the ship's hull before rescue teams were able to remove the remaining fuel.

In the days after the accident, thousands of volunteers scoured the shoreline in rubber boots and gloves to clean the beaches and tie makeshift cords to stem the oily tide.