The blast on an oil tanker in Saudi Arabia was reportedly caused by an “external source”.

An oil tanker exploded early Monday in the Saudi port city of Jeddah, hitting an “external source”, a shipping company said, adding that another ship had come under state attack during years of fighting in Yemen.

The BW Group said in a statement that it had rescued all 22 sailors without injury. The company warned that a small amount of oil could leak out of the blast site.

Saudi Arabia did not immediately respond to the blast, which struck at a crucial port and distribution center for its oil trade. However, it comes after a mine attack last month damaged a Saudi Arabian tanker, which officials blamed on Yemen’s Houthi rebels.

The United Kingdom Marine Trade Operations, an organization under Britain’s Royal Navy, urged ships in the area to be vigilant and said an investigation was under way.

A maritime intelligence company called Dryad Global also reported the blast. No one immediately gave a reason.

U.S. The Navy’s 5th Fleet, which patrols the Mediast, did not immediately respond to a request for comment.

The blast came after a mine exploded in Saudi Arabia last month and damaged a ship. Another mysterious attack earlier this month targeted a cargo ship near the small port city of Nishchun in eastern Yemen.

Yemen’s Iranian-backed Houthi rebels have used sea mines for the first time in a long war against a Saudi-led coalition. However, the Houthis have not commented on last month’s attack.

If those huts were behind Sunday’s eruption, it would “represent a fundamental change in both target capability and purpose,” Dryed Global said.

The Red Sea is an important shipping lane for both cargo and global energy supply, making any mining in the region a threat not only to Saudi Arabia but to the world as a whole. Mines can enter the water and then be carried into the Red Sea by the changing currents of season tu.

The Red Sea has been mined before. UN investigators of war in Yemen According to the panel, in 1984, as many as 19 ships reported striking mines there, with only one recovered and disarmed, according to the UN, which is investigating the war in Yemen.