The shipments transited on six crude carriers that had their AIS data switched off.

A US blockade of Iranian ports came into effect on April 13.

The blockade, Vortexa said, “is not necessarily implemented close to Iranian ports nor within the Strait of Hormuz, but flexibly around an area about 300 miles to the West between the Pakistani/Iranian border and the most western ‘corner’ of Oman.”

Vortexa recorded 35 total transits through the US blockade from April 13 to 22, involving Iran-linked or sanctioned vessels for inbound and outbound journeys.

Since the blockade took effect, Iran-linked traffic through the Strait has fallen, averaging 1 to 2 tankers per day between April 13 and 21, down from around 2 to 3 per day over the previous 30 days.

The US military intercepted at least three Iranian-flagged tankers in Asian waters, shipping and security sources said on Wednesday.

The US military said on Wednesday afternoon ⁠that it had so far directed 29 vessels to turn around or return to port as part of the US blockade against Iran.