A critical incident has been declared at the Port of Dover after 15 asylum seekers were found in a tanker on a cross-Channel ferry.
They were discovered on P&O's Spirit of France and two have been taken to hospital amid inquiries to discover whether any hazardous substance was on board.
None of those found in the tanker was in a life-threatening condition and two drivers have been held in custody, a Port of Dover Police spokeswoman said.
Ferry services have not been affected by the alert at the Kent port's Eastern Docks and the port remains open as emergency teams continue inquiries.
A Port of Dover Police spokesman said: "The Port of Dover can confirm that a critical incident is under way concerning 15 asylum seekers found in a tanker on board P&O's Spirit of France. Emergency services are at the scene and are dealing with the situation in close co-operation with port staff. Thirteen of the asylum seekers are non-critical but two have been taken to hospital. Two drivers are in custody. The port is open. Ferry services are currently unaffected."
Kent Fire and Rescue Service said it sent six fire engines and some specialist equipment to the scene. It said: "Kent Police, SECAmb (South East Coast Ambulance Service), the Border Control Agency and the HMRC are also in attendance and dealing with the situation in close co-operation with port staff."
Along with its sister ship Spirit of Britain, Spirit of France is the largest ferry built for the Calais-Dover crossing. It weighs more than 47,000 gross tons and is more than 213m long. A P&O spokesman said the Spirit of France would be delayed by the incident but it is expected to resume sailing by the end of Wednesday morning. He said: "P&O Ferries is helping the police with their investigations into the incident involving the Spirit of France."
Examination of the tanker was continuing but police said a powder found on board was non-hazardous, the police spokeswoman added.
A SECAmb spokesman said two people were taken to the William Harvey Hospital in Ashford. He said: "We didn't have any reports of anyone in a life-threatening condition but the people needed to be checked over, with some having minor breathing difficulties and chest pains. We sent a total of eight vehicles, of which three were ambulances."
It is understood that the asylum seekers were found after banging was heard from the sides of the lorry as the 7.45am Calais-Dover ferry berthed at the port. Kent Fire and Rescue Service said it was scaling down its operations at the port and handing the incident over to police. A Border Force spokeswoman said: "Border Force is working with Kent Police, Kent Fire and Rescue Services and South East Coast Ambulance Services at an incident in Dover's Eastern Docks. "It follows the discovery of a number of suspected illegal migrants on board a lorry."