Police are dealing with an “ongoing incident” on board an oil tanker situated off the Isle of Wight.
The crude oil tanker, the Liberian-registered Nave Andromeda, is thought to have stowaways on board and was due to dock in Southampton earlier.
Lawyers Tatham and Co, representing the vessel’s owners, said the incident was “100% not a hijacking” despite reports.
Hampshire Constabulary said the vessel was currently situated south of the Isle of Wight.
The owners’ lawyers said it had been known for a while there were stowaways were on board.
The Maritime Coastguard Agency said it was assisting police and search and rescue helicopters were at the scene.
The Ministry of Defence has told the BBC that there is no military involvement in the operation.