A suspected oil spill covering dozens of square kilometres of sea near Iran’s main oil hub of Kharg Island has been seen on satellite imagery this week, Reuters reports.

The likely spill — appearing on images as a grey and white slick — covered waters to the west of the 8-kilometre-long island, pictures from Copernicus Sentinel-1, Sentinel-2 and Sentinel-3 satellites showed from May 6-8.

The slick appears visually consistent with oil, says Leon Moreland, researcher at the Conflict and Environment Observatory, who estimates that it covered an area of approximately 45 square km.

Louis Goddard, co-founder of consultancy Data Desk, which focuses on climate and commodities, agrees that the images likely show an oil slick, which he said was potentially the largest to occur since the start of the US-Israel war against Iran 70 days ago.

The US military and Iran’s mission to the United Nations in Geneva did not immediately respond to requests for comment on the images.

The cause of the possible spill and the point of origin are currently unknown, Moreland adds, noting that images from May 8 showed no evidence of additional active spills.