An oil spill at an Exxon Mobil platform in the Bass Strait is being investigated by the federal regulator, after the discovery of an oily sheen on waters around the rig.

The spill comes less than 18 months after a fire raged on the same platform for nine hours before it could be controlled. And in 2013, Exxon was responsible for a spill from another rig in the Bass Strait.

Environmentalists have said the spill is a reminder of the inherent dangers of offshore oil drilling, and called for planned oil drilling in the Great Australian Bight to be stopped.

North Sea or Great Australian Bight, oil drilling is always a risky business

On Thursday, the National Offshore Petroleum Safety and Environmental Management Authority (Nopsema) posted an alert saying Esso, a company owned by ExxonMobil, had informed it of an oil sheen alongside its West Tuna platform in the Bass Strait the previous day.

The platform is 45km off the Gippsland coast in Victoria. The cause of the spill, and how much oil contaminated the water, was not yet known.

A spokesman for ExxonMobil said it was still investigating the cause of the spill.

“On Wednesday, 1 February an oil sheen was observed on the water near the West Tuna platform in the Bass Strait,” he said. “Esso responded immediately and continues to investigate potential sources of the sheen observed on 1 February.

“The Tuna to West Tuna pipeline, which is the pipeline nearest to the observed sheen, was shut-in at the time of original observation due to planned maintenance on West Tuna platform and remains shut in and not in operation.”

The Greenpeace oceans campaigner, Nathaniel Pelle, said: “Offshore oil drilling is risky business for our oceans and fisheries industries, as this latest oil spill near one of Australia’s largest fisheries shows.

“This spill in the Bass Strait should send a clear ‘wrong-way-go-back’ signal to the federal government, which is set to consider exploratory oil drilling by Chevron in the Great Australian Bight – a nursery for southern right whale calves.”

In September 2015 an electrical fire raged for nine hours on the same rig. It caused all the lights on the platform to go out, forcing an evacuation to occur at night without lights.

In 2013, another ExxonMobil rig in the Bass Strait spilled about 750 litres of oil into the water.

The Exxon spokesperson defended the company’s safety procedures.

“Our platforms and pipelines are operated in accordance with ExxonMobil’s operations integrity management system, together with regulator approved safety cases and environmental plan which are systems to ensure the safety and health of personnel, maintain facilities integrity, and protect the environment,” he said.

Copyright: The Guardian