Iran’s oil exports may be only 4% of the level of April 2018, according to an industry source and tanker data.

Reuters reports that Tehran’s official exports in July could be as low as 100,000 barrels per day, compared to 2.5 million bpd 17 months ago, amid comprehensive US sanctions from November.

Initially after the imposition of the restrictions, Iran was able to sell about 1 million bpd. But the sanctions were tightened this spring, with the US ending waivers for the Islamic Republic’s largest customers such as China, India, Japan, South Korea, and Turkey.

An industry official and the tanker tracker Refinitiv Eikon estimated sales at 100,000 bpd this month and about 120,000 bpd if condensate, a light oil, is included. Another analyst, Sara Vakhshouri, said the most that Iran can now export is between 225,000 and 350,000 bpd, less than the 400,000 bpd which was shipped in June.

Other analysts have said that Iran is moving some oil — some have said up to 400,000 bpd — on the grey or black market, with tankers avoiding trackers.

A report in late June said China took its first delivery of Iranian crude since the US ended sanctions waivers, with a Suezmax tanker offloading up to 1 million barrels.

See Iran Daily, June 27: China Defying US Sanctions on Tehran’s Oil Exports

But industry specialists says Iran’s situation had worsened because of tension over attacks on tankers in and near the Strait of Hormuz, which carries 1/6th of the world’s oil.

Tankers in the Gulf of Oman and in a UAE port have been attacked with explosives. Earlier this month Iran’s Revolutionary Guards seized a UK-flagged, Swedish-owned tanker, retaliating for Britain’s impoundment of an Iranian supertanker off the coast of Gibraltar.

See Iran Daily, July 29: UK Rejects Tanker Swap

Kpler, a company which tracks oil flows, said Iran loaded another 417,000 bpd of crude and condensate onto tankers in July. The amount in tanker storage is now 56 million barrels, double the level of May, and about the same volume held in tanks on land.