A preliminary probe has concluded that a "state actor" was likely behind the sabotaging of four oil tankers off the coast of the United Arab Emirates in May, according to RT. This comes after the United States put the blame "squarely" on Iran.

Preliminary findings from the investigation, which was jointly concluded by the UAE, Saudi Arabia and Norway, describe the attack as a "complex effort that required significant resources". The findings do not make mention of Iran.

Investigators instead argue that attackers that inflicted damage on the tankers required a "high degree [of] sophistication," precise intelligence, and "expert navigation of fast boats" to pick the targets and get in and out undetected. The investigators claim that these signs mean a "state actor" was likely responsible. The attackers did not cause casualties or an oil spill.

The wording of the investigation allows the countries behind the report to maintain a neutral image without actually contradicting Washington, who had directly accused Iran.

US National Security Advisor to the president John Bolton said last month that the attacks were "almost certainly" perpetrated by Iran, accusing it of planting "naval mines" under the ships. It is unclear whether or not Bolton's assertion has been based on any intelligence.

The attack took place off the coast of the UAE emirate of Fujairah, which lies outside the Strait of Hormuz. The area is immensely important for the transportation of oil and tankers carrying crude from Gulf countries must pass through it.

Iran had previously threatened to block oil shipments through the waterway in response to the United States' intention to bring Tehran's oil exports to "zero". Meanwhile, the United States has recently declared Iran’s elite Revolutionary Guard a terrorist organization and sent an aircraft carrier group to the Gulf, possibly telegraphing a coming boost to the number of American troops in the region.

The four commercial tankers targeted on May 12 included two from Saudi Arabia, one Emirati and one Norwegian ship. Iran has dismissed accusations that it was involved, calling John Bolton's statement "ridiculous".