One day Samir Madani, a Kuwaiti oil trader living in Sweden, noticed something strange. He had always been captivated by oil and its influence on political relations, in peacetime and wartime, so much so that he created the website TankerTrackers.com.

Some might think that watching tankers is boring, given that they usually coast along predetermined routes. But in November 2017, Madani noticed that the oil tanker Valtamed, heading to the Suez Canal from the Turkish port of Ceyhan – which is supplied by the oil pipeline from the Kurdish areas of northern Iraq – suddenly stopped somewhere in the eastern Mediterranean, off Tel Aviv but outside Israel’s territorial borders, and turned off its identification transponder. When it “resurfaced” a few days later, it was lighter, Madani realized.

After mysteriously growing lighter off Israeli shores, the Valtamed sailed to Cyprus, returned empty to its home base in Turkey, loaded up on oil that had arrived from northern Iraq and repeated the whole journey, including the disappearing act. Madani understood that this was something bigger than just a ship going haywire.

His conclusion was that the Valtamed had been shipping oil that wasn’t recorded anywhere to a country that wasn’t supposed to buy it – in other words, Israel was secretly buying Kurdish oil through Turkey.

The incident was described by Ellen Wald in the Cairo Review of Global Affairs, which is published by the American University in Cairo.

Wald points out that oil has been bubbling from the ground in Baba Gurgur in northern Iraq since prehistory, and was “officially” discovered in 1927. The field turned out to be one of the world’s largest, with low production costs, but the Kurdish oil still needed to be refined and reach the sea. In 1934 the British built a 950-kilometer pipeline to bring the oil to a refinery in Haifa, but the pipeline stopped operating once Israel was established in 1948. For years the oil from northern Iraq has been sold through a different pipeline, one going from Kirkuk to Ceyhan.

Everybody covets this black gold. It took a Kuwaiti observer in Sweden to figure out how Israel was getting it. TankerTrackers says a tanker called Kriti Diamond tends to suddenly assume a new identity – Kiton – offload oil in Israel and then resume its original identity before sailing back to Turkey. “It is with great pride that we present you the missing KRITI DIAMOND, currently operating under her new pseudonym: KITON,” the site tweeted on February 16.

Four days later, it was followed by another tweet: “The MARIKA/KRITI DIAMOND forgot to take off her disguise as KITON after leaving Ashkelon empty.”

TankerTrackers noticed that another crude oil tanker, the Mabrouk, left Ceyhan, assumed the disguise of Maro – an unknown, unregistered identity – near the Israeli shore, disappeared for a few days and then popped up again as the Mabrouk.

When asked for a response, Oil Refineries in Haifa and the Trans-Israel Pipeline company said they do not comment on commercial matters.