The Royal Gibraltar Police on Friday said that it had arrested four Indians aboard the Iranian Grace 1 tanker that had been detained last week after being suspected to have broken European Union sanctions by transporting oil to Syria, Reuters reported.

“All four men are Indian nationals and they have been granted full legal assistance,” Gibraltar police, British Overseas Territory on the Spanish coast, said in a statement. The authorities also said that the arrested were being provided consular access.

The police said the Indian High Commission in the United Kingdom had been informed. A Royal Gibraltar Police spokesperson said that the Indians were being questioned and the investigation was going on, but “they have not been charged”, according to PTI.

The Indian High Commission in London said that it had been in touch with the authorities and “consular access has been sought and all assistance will be provided to the Indian citizens”.

The tanker was carrying crude oil from Iran to the Baniyas Refinery in Syria in violation of the sanctions imposed on the latter. It was detained by the Gibraltar port and law with the help of Britain’s Royal Marines.

Meanwhile, the United Kingdom on Friday decided to send a second warship to the Gulf amid escalating tensions with Iran, BBC reported. Iran’s Foreign Ministry Spokesperson Abbas Mousavi said Britain was getting involved in a “dangerous game”.

“This is a dangerous game and we advise them not get involved in this game under America’s influence,” PTI quoted him as saying. “We ask them again to release the tanker immediately, which will be in all countries’ interest.” Earlier, Iran had claimed that the tanker was not headed for Syria, and had threatened to seize a British oil tanker in response.

British Overseas Territory’s Chief Minister Fabian Picardo said in the Gibraltar Parliament that the decision was taken independently. “These important decisions about breaches of our laws were not decisions taken at the political behest or instruction of any other state or third party,” he said.

On Wednesday, Iranian President Hassan Rouhani had warned the United Kingdom of consequences after Britain seized the oil tanker bound for Syria off the coast of Gibraltar last week. Iran also blames the United States for getting its ship seized due to the sanctions Washington has imposed on Tehran in the attempt to stop its oil exports.

European countries have not placed sanctions against Iran, however, they have imposed them on Iran’s ally Syria since 2011.