Seven men have been arrested on suspicion of attempting to hijack the oil tanker that was stormed by members of the Special Boat Service (SBS) off the coast of the Isle of Wight on Sunday night. Hampshire police said they had detained the men – who are understood to be Nigerian nationals – for allegedly “seizing or exercising control of a ship by use of threats or force”. The seven are being held at police stations across the county, where they are being questioned. The SBS, operating at the request of Hampshire police, seized control of the Nave Andromeda and secured the crew in an operation lasting around nine minutes on Sunday evening. Navios Tanker Management, the Greek company that owns the vessel, said stowaways had boarded the tanker in Lagos, and that as the ship approached England its captain had radioed seeking help. “The UK authorities had been advised by the master that stowaways had been found on board and that he was concerned for the safety of the crew due to the increasingly hostile behaviour of the stowaways,” Navios said in a statement. Hampshire police said the men had been arrested subject to section 9(1) and (3) of the Aviation and Maritime and Security Act 1990. Officers will consider whether there is enough evidence to bring criminal charges against some or all of them, and whether to seek to deport them. It remains unclear precisely what happened on the vessel on Sunday. One source said crew members locked themselves in the control room of the ship for their own safety until the special forces arrived. Defence sources sought to justify the deployment of the SBS, part of Britain’s special forces. One insider said a “threat to life” had been communicated and was “believed to be a very real possibility”. A recording of the mayday call made on an open channel by the ship’s captain and obtained by the Times suggests he feared the tanker’s control room was surrounded, saying he saw “four persons port side” and “two of them starboard side” of the bridge. “I try to keep them calm, but I need immediately, immediately agency assistance,” the captain said. On Sunday night, the Ministry of Defence described the situation onboard as “a suspected hijacking”. But Bob Sanguinetti, the chief executive of the UK Chamber of Shipping, said he thought that was not the case. “Nothing at this stage suggests that this was hijacking, and in fact hijacking of this nature is extremely uncommon,” he told the BBC. Chris Parry, a retired rear admiral, said: “They will have wanted to send a message here: if you try to take control of a tanker, there will be a response.” The 228-metre tanker had been expected to dock in Southampton on Sunday to pick up a cargo of petrol, but its course in the Channel became erratic, prompting calls for an intervention as it passed the south-east coast of the Isle of Wight. The SBS, based in Poole, Dorset, is the unit trained to deal with incidents at sea. Commandos from the unit were deployed and the tanker was reported by the MoD as being secured at 8.15pm. Hampshire police said on Sunday that all 22 crew of the Nave Andromeda were safe and well. The vessel left Lagos on 6 October and made two stops on its voyage, anchoring off the Canary Islands and off the French coast just south of Saint-Nazaire in Brittany. The incident comes after a summer in which the number of migrants crossing the Channel has rapidly increased. According to a PA Media analysis, by the end of September 7,000 migrants had arrived in the UK in small boats this year – more than three times the number of arrivals by the same route in the whole of 2019. Incidents such as the one on Sunday are extremely rare, and it is unclear if the seven men had planned to try to claim asylum in the UK before the ship was seized. In January four stowaways who secretly boarded a ship in Nigeria in 2018 were jailed for affray and two of the four were also found guilty of threats to kill. A court heard that they “ran amok” on the container ship and demanded to be dropped off in the UK when the ship reached the Thames estuary. During the trial, the judge, Nigel Lickley QC, said it was an “unusual case” the like of which he had never come across before.