THE HAGUE (AFP) - A Dutch ferry crew found 25 migrants in a refrigerated container on a boat sailing to Britain on Tuesday (Nov 19) and forced the vessel to return to port in the Netherlands, police and emergency services said.

The stowaways received medical attention at the port of Vlaardingen, near Rotterdam, with two being transferred to hospital for more care, they said.

"On board a ship it turned out that several people were found in a cooling container. The ship returned to the harbour," said the Rotterdam region emergency services said on Twitter.

"The 25 people were taken off the ship and given the medical care they need. Earlier the message came from the ship that no people died."

Police dogs were searching the ship, which was originally bound for the British port of Felixstowe, to check that no more migrants were on board, they added.

A large number of ambulances and other emergency vehicles could be seen near the busy port, Dutch media reported.

The boat was a cargo ferry run by the DFDS Seaways line, which said that the migrants had come on board on a lorry trailer, De Telegraaf newspaper said.

The discovery comes the month after 39 Vietnamese people were found dead in a refrigerated truck in Britain last week, again laying bare the risks of illegal migrant routes to Europe.