The UK Border Agency has refused to comment on the fate of two men, believed to be illegal immigrants, who are reported to have gone overboard from a passenger ferry just off the coast of Harwich.

The men who were said to have jumped from the ferry, sparking a major air-sea search and rescue operation off the Suffolk coast, have still not been found. Mystery surrounds the disappearance of the men, who were believed to be being deported, and a thorough search took place of the Stena Britannica when it arrived at the Hook of Holland.

However Border Agency officials are refusing to comment on the incident until the situation had been clarified.

Thames Coastguard received a call just before 10am on Wednesday from a passenger on the vessel, which had left Harwich shortly beforehand, concerning reports that two men had gone overboard about one mile from Harwich Harbour.

Around 20 vessels and two helicopters – Suffolk Constabulary’s and the rescue helicopter from Wattisham Airfield – were sent to the scene off Felixstowe.

Three RNLI lifeboats – two from Harwich and one from Walton – along with tugs, a pilot cutter, and fishing boats took part. The Stena Britannica also searched the area, making about four turns around the bay.

Shipping in the wider area was also asked to keep a look-out.

On the shore, land-based Coastguard rescue units from Felixstowe and Shingle Street searched the coastline between Old Felixstowe and Landguard, and the banks of the River Orwell and Deben estuaries.

A Coastguard spokeswoman said search and rescue plotting was used with teams searching the exact location where the men were reported to have gone overboard, taking account of tide patterns and speeds, to pinpoint where they would be in the water, and then fanning out to cover a wider area.

She said: “After three hours the search mission co-ordinator decided the area had been thoroughly searched and saturated with units and the decision was taken to stand down until any new information was received.

“Investigations are ongoing with the police and the ferry company to determine exactly what happened. The circumstances as far as we are concerned were that there were two people in the water and a search was launched but we found nothing at all.”

The Border Agency refused to comment until the details of the incident had been clarified and the identities established of the two people involved.

A spokesman could not say if the deported men would have been accompanied on the ship by Border Agency officials.

The Stena Britannica, which has 92 passengers and 81 crew onboard, was released at lunchtime to resume its North Sea crossing.

A spokesman for Stena Line said: “The two passengers are believed to have jumped overboard at approximately 9.45am.

“The passengers were travelling on the Stena Britannica and the incident occurred off the coast of Felixstowe.

“Stena Line cannot yet confirm the identity of the two passengers.”