Cleveland Police have said they have been given an extra 12 hours to question back-from-the dead canoeist John Darwin.

The news comes after Anne Darwin left Panama on Wednesday night and is making her way back to Britain.

The couple were communicating by telephone and applying for credit cards to fund a new life abroad, investigators believe.

Inquiries into the supposed death began several months ago when Mrs Darwin was overheard by an acquaintance speaking to her husband on the phone, a police official said.

Police are investigating the possibility Mr Darwin has been in hiding in the US since 2002, the official said, since the calls in question came mainly from the US and Panama.

Meanwhile, Mr Darwin's sons have spoken about their "anger and confusion".

In a statement, Anthony and Mark Darwin said: "Having seen the recent media speculation surrounding our parents ever since our dad was arrested, we are very much in an angry and confused state of mind.

"In the short space of time following our dad's appearance in London on Saturday, we have gone through a rollercoaster of emotion.

"From the height of elation at finding him to be alive to the depths of despair at the recent stories of fraud and these latest pictures. And the shock of being thrust into the media spotlight.

"If the papers' allegations of a confession from our mam are true then we very much feel that we have been the victims in a large scam.

"How could our mam continue to let us believe our dad had died when he was very much alive?

"We have not spoken to either of our parents since our dad's arrest and at this present time we want no further contact with them.

"Cleveland Police have asked for anyone with knowledge of our dad's whereabouts over the last five years to come forward and we support this wholeheartedly.

"We too want to know where he has been and what he has been doing.

"We have been in constant contact with the police and will be helping them with their enquiries in any way we can."

The 57-year-old is being held at Kirkleatham police station after he was arrested on suspicion of fraud at his son Anthony's home in Basingstoke, Hampshire.

The police station stands a few miles outside Middlesbrough, across the Tees estuary from Seaton Carew where Darwin was reported missing five-and-a-half years ago.

© Independent Television News Limited 2007. All rights reserved.