Mr Darwin was arrested in the early hours
A canoeist who reappeared five years after it was thought he had drowned has been arrested on suspicion of fraud.
John Darwin, 57, was presumed dead after the remains of his canoe were found on a beach in Seaton Carew, near Hartlepool, Teesside, in March 2002.
He walked into a London police station at the weekend saying he did not remember where he had been.
His arrest came as the Daily Mirror published a photo allegedly showing Mr Darwin and his wife, Anne, in Panama.
There has been no independent verification of the photograph, said to have been taken in an apartment rented through the firm Move to Panama, in 2006.
Det Supt Tony Hutchinson said the validity of the photo was an important part of the investigation.
Police revealed they have been investigating Mr Darwin's disappearance for three months.
Cleveland Police issued a worldwide appeal for help in tracing his movements over the past five years and said Mr Darwin appeared tanned and well when he spoke to officers.
He was arrested at the home of one of his sons in Chineham, Hampshire.
Anne Darwin has moved to Panama
Det Supt Hutchinson said Mr Darwin's reappearance had "raised a lot of questions".
He made a public appeal for information, telling reporters: "There will be people out there who know exactly where he has been, what he has been doing and where he has been living.
"There was some information which was reported to us three months ago to suggest that perhaps there was something suspicious with regards to his disappearance and as a result of that information we then began to conduct some inquiries on a financial basis.
"Certainly three months ago we did not know that John Darwin was alive and we did not know that until he walked into the police station on Saturday morning."
Det Supt Hutchinson stressed that an extradition treaty existed with Panama and that Mrs Darwin may be interviewed in the future.
He said: "Without doubt, this is an unusual case. However, there will be people out there who know exactly where he has been, where he has been living, and what he has been doing.
"And certainly my appeal today would be for anybody who has any information whereby we can piece together what has happened over these last five years, if they could contact us."
Mr Darwin, who was reunited with his sons Anthony and Mark earlier this week, said he could not remember anything since June 2000.
Mrs Darwin, who moved to Panama several weeks ago, told the Daily Mail newspaper she claimed her husband's life insurance payouts in good faith after he had been declared dead by a coroner in 2003.
She added that money may now have to be repaid.
In the statement issued earlier through Cleveland Police, Anthony, 29, and Mark, 31, said that the news of their father's appearance had come as a huge shock to the whole family, but they were extremely happy.
They said he appeared to be in good health and that his wife had been informed and was delighted at the news.
They added: "Since Saturday evening we have been through a traumatic and emotional time and this continues to be a stressful time for John and the family."
Mr Darwin's 80-year-old aunt Margaret Burns, from Blackhall Colliery, County Durham, said: "We don't know the truth of the story, but I think we will if we wait a bit.
"But what's the point in speculating, when we don't know? I'm as intrigued as anybody about what happens next.
"Most of the family believe the trauma of nearly drowning in the canoe was enough to make him lose his memory, but I'm not so sure."