Two vessels loaded with liquefied natural gas (LNG) from Ras Laffan, Qatar, turned back after they moved eastward towards the Strait of Hormuz, ship-tracking data showed on Monday.

Had the vessels successfully crossed the strait, it would have been the first transit of LNG cargoes through the waterway since the U.S.-Israel war with Iran began on Feb. 28.

Data from analytics firms Kpler and LSEG showed the vessels, Al Daayen and Rasheeda, loaded their cargoes in late February. The data also indicated that the Al Daayen tanker was signaling for China at the moment.

Additionally, Kpler data showed both tankers as controlled by QatarEnergy.

QatarEnergy did not immediately respond to a Reuters request for comment. Previously, a Japanese LNG tanker, the Sohar LNG, managed to cross the strait, its joint owner Mitsui O.S.K. Lines said on Friday. The tanker, however, was empty, and a company spokesperson declined to disclose when the passage took place or whether any negotiations were involved.

It has been more than five weeks since the U.S. and Israel began striking Iran in a war that has killed thousands and damaged economies by driving up oil prices, with tanker traffic through the Strait of Hormuz choked by the fighting and retaliatory attacks on a route that carries about a fifth of global oil and LNG flows.

Qatar is the world's second-largest exporter of LNG, with shipments mostly going to buyers in Asia. Iranian attacks, however, knocked out 17% of Qatar's LNG export capacity, with repairs expected to sideline 12.8 million tons per year of the fuel for three to five years.