The Gibraltar police said they had arrested the captain and the chief officer of the Iranian supertanker Grace 1, accused of violating EU sanctions in Syria and of seizing electronic documents and devices from the ship.
Last week the British Royal Marines boarded the Gibraltar oil tanker and seized it with the accusation of having broken the sanctions of the European Union by bringing oil to Syria.
"Investigations are still ongoing and Grace 1 continues to be detained," police said in a statement on Thursday.
The two men, both Indian nationals, were arrested Thursday afternoon and interviewed.
Nor have they been accused, according to reports.
According to Gibraltar chronicle, Royal Gibraltar police said the arrests followed "a long search for the ship where electronic documents and devices were seized and examined".
Arrests come after Iranian boats tried to seize a British oil tanker in the Gulf.
Three ships, believed to belong to the Iranian Revolutionary Guard, approached the tanker as he sailed across the Strait of Hormuz.
But the British warship HMS Montrose, which reportedly had its 30mm guns trained on boats, warned them by radio.
It arrives after Iranian President Hassan Rouhani said that Britain would face "consequences" for the seizure of an Iranian tanker.
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