The tracker said on Tuesday crude shipments remain trapped inside the blockade zone despite some refined fuel cargoes escaping sanctions pressure.
“To our best knowledge, Iran hasn't successfully exported any crude oil by sea over the past 28 days,” the monitoring firm said on X, adding that its definition of an export is a tanker successfully crossing the US Navy blockade line without returning with the cargo.
The group said some refined petroleum products had still managed to leave Iran because the US Treasury’s Office of Foreign Assets Control (OFAC) had not sanctioned the tankers involved.
It also reported that multiple empty and loaded tankers remain clustered near the blockade perimeter and in waters not far from Pakistan.
The United States began enforcing a naval blockade on Iranian ports and oil exports on April 13 as part of its broader pressure campaign against Tehran during the ongoing conflict.
Washington has said the measures are aimed at restricting Iran’s oil revenues and limiting its ability to finance military operations and regional armed groups.
Kharg oil spill
Tanker Trackers said Kharg Island, the hub for 90% of Iran's oil exports, has not loaded any tankers since May 6 as a result of an oil leak which Tehran denied taking place.
Satellite images last week showed the suspected oil spill spreading across dozens of square kilometers of water near Kharg Island.
The likely spill, visible as a gray-and-white slick, appeared west of the five-mile-long island in images taken by Copernicus Sentinel satellites between May 6 and May 8 seen by Reuters.
Leon Moreland, a researcher at the Conflict and Environment Observatory, said the slick looked visually consistent with oil and estimated it covered about 45 square kilometers.
Louis Goddard, co-founder of climate and commodities consultancy Data Desk, also said the images appeared to show an oil slick, potentially the largest since the US-Israel war against Iran began in late February.
The cause and origin of the suspected spill remain unclear, Moreland said, adding that May 8 images showed no sign of further active spills.