Seven suspects have been detained, and the crew of the vessel, the Nave Andromeda, are reported to be safe and well, according to a ministry statement.
The ship, off the coast of the Isle of Wight, had been “subject to suspected hijacking,” the statement said.
British police officers earlier said they were responding to an incident involving stowaways on board the tanker.
Several stowaways made verbal threats to the crew on board the tanker, the UK’s Hampshire police told CNN.
“Concerns were raised to police for the welfare of crew on board the Nave Andromeda” Sunday at 10:04 a.m. GMT (6:04 a.m. ET), Jack Backwell, a police spokesman, said in an email to CNN.
“Police are currently working closely with our partners, including the Maritime & Coastguard Agency and Border Force, to bring this incident to a safe conclusion,” Backwell said, adding that “an exclusion zone, with a three-mile radius, is currently in place near the vessel.”
The 750-foot (228-meter) vessel is registered in Liberia, according to PA Media. The tanker was south of the island, police said earlier.
Further details of the incident remain unclear. The British PA news agency has cited reports of an attempted hijacking by stowaways.
Local lawmaker Bob Seely earlier suggested the vessel may now be controlled by stowaways, during an interview with Sky News on Sunday.
“Isle of Wight Radio are reporting — and they’ve got very good contacts in the Coastguard — that despite being told not to drop anchor, the skipper has dropped anchor and the ship may be now under the control of stowaways on the ship,” Seely said.
Two Coastguard helicopters were sighted circling around the vessel, according to Isle of Wight Radio, which also reported that a three-mile exclusion zone has been placed around the area south of Sandown on the island’s east coast.
Instead, the vessel made several zig-zag maneuvers just off the Isle of Wight within a few hours.
Bob Sanguinetti, chief executive of the UK Chamber of Shipping, told Sky News that the zig-zagging “could well have been a way of alerting the authorities.” The vessel would also have been in touch with authorities via radio, though, he said.
He said “the uncertainty here is over the motives of the stowaways and, like I said, it could be nothing more sinister than seeking political asylum.”
Fifteen to 20 crew members would be on a ship of this size, Sanguinetti said.
The Maritime & Coastguard Agency said in a statement that it was assisting Hampshire Constabulary, and it had search and rescue helicopters present.
CNN’s Nina Avramova, Sarah Dean and Jonny Hallam contributed to this report.