(Bloomberg) -- An abandoned oil tanker attacked in the Red Sea by Iran-backed Houthi rebels a week ago appears to be burning and leaking, raising the specter of environmental disaster, a Pentagon spokesman said on Tuesday.

The comments are the latest to underscore what the European Union’s navy in the region described as an imminent environmental hazard and a potentially severe ecological disaster.

The 900-foot Sounion was hauling 150,000 tons of dense Iraqi crude oil when it was disabled by Houthi militants last week. The crew were rescued and on Friday further fires were spotted on board. Yemen’s Houthi militants subsequently released a video showing an attack and explosion.

The images show the challenges of dealing with environmental damage in an area that maritime insurers deem a war-like area. The Pentagon has said the Houthis warned off salvage teams from approaching the tanker, and so far the militants haven’t made any public statements to suggest that they’d be safe to approach the stricken ship.

In an absolute wost-case scenario where all of its cargo leaked, the Sounion would represent the fifth largest spill on record — more than previous recent incidents like the Sanchi spill near China and far more than the Exxon Valdez. There is no suggestion at this stage that such an outcome is likely but it’s nevertheless unclear how a leak could be dealt with.

Modern oil-carrying vessels have multiple tanks and two hulls to try and limit any potential spills, and it’s unclear what the actual leak might be.

“Sounion now sits immobilized in the Red Sea, where it is currently on fire and appears to be leaking oil, presenting both a navigational hazard and an environmental catastrophe,” Maj. Gen. Patrick Ryder said in a news briefing.

Merchant ships crossing the Red Sea have been frequently targeted by the Houthis since last year, when Iran-backed militants stepped up their retaliation to Israel’s activities in Gaza. Thousands of ships from container vessels to oil tankers have opted to avoid the area, though a handful of shipowners remain happy to run the gauntlet.

Warned Away

According to Ryder, two tug boats were sent by a third-party entity to the burning Sounion to help with salvage, but they were warned away by the Houthis. US central command is actively monitoring the situation and coordinating with maritime partners on how best to assist the vessel, he added.

“Clean-up and remediation will be difficult, as Houthis threaten to attack any supporting vessels, while they themselves have limited capacity to deal with oil spills on the shores of Yemen,” said Wim Zwijnenburg, a project leader at Netherlands-based PAX who’s spent 10 years studying satellite images to identify the environmental impacts that conflicts cause.

His analysis is that it is engine oil that’s leaking, although heavy cloud and smoke plumes have made assessment of satellite imagery difficult, he said.

The tanker was hired by the Greek oil refiner Motor Oil, according to people with knowledge of the matter, who asked not to be identified because the information isn’t public. The Athens-based company didn’t immediately respond to requests for comment.

Near Eritrea

The Pentagon statement is the first official mention of a likely leak, after the European Union naval forces in the region said earlier this week that there were no obvious signs of a spill.

Satellite imagery monitored by Bloomberg from Aug. 25 shows the tanker was on fire in the southern Red Sea, about 90 miles west of the Yemeni port city of Hodeidah and about 40 miles from the coast of Eritrea to the southwest.

Two separate plumes of dark smoke can be seen rising from the ship, one from near the stern, to the starboard side of the bridge, and a second that appears to be coming from a forward cargo tank.

The International Maritime Organization, the UN’s shipping watchdog, said it is monitoring the incident after an operation to remove the oil from a decrepit 47-year-old ship near Yemen last year.

“We are following the situation and gathering as much information as possible,” a spokesperson said by email. “IMO is able to provide technical support to governments facing a significant oil spill, upon request.”

It said it is currently communicating with national and regional entities, as well as the UN, about any such potential request for support.

If there is a spill from the ship, member states won’t be eligible to receive a payout form the International Oil Pollution Compensation Funds, a spokesperson said. Such payments are exempt when there’s damage that results from acts of war, hostilities, civil war or insurrection, they added.

The vessel is owned and operated by Greek shipping company Delta Tankers. Its crew was evacuated a day after the attack with assistance from the French navy. Two other ships owned by the company had been targeted earlier in the month, according to a report from naval forces in the region.

Asked about a possible leak, a spokesperson for Delta tankers referred to a previous statement.

That said the company “is doing everything it can to move the vessel (and cargo). For security reasons we are not in a position to comment further.”

--With assistance from Serene Cheong, Julian Lee, Jack Wittels and Rachel Graham.