Police have urged people to hand in banknotes found in the street after £1,600 was thrown away by a robber.
A man threatened staff at Barclays in Jewry Street, Winchester, at about 1020 BST before discarding the cash outside for unknown reasons.
Hampshire Police thanked those who had already handed notes in, but urged others who had found the cash to take it to a police station as evidence.
A Southampton man, 42, was arrested on suspicion of robbery and is in custody.
Police said the robber had claimed he was armed during the raid but no evidence of this has been found.
Det Insp Andy Symes said: "The man left the bank, and a short time later threw the money into the street for reasons we have yet to establish.
"We would ask that any members of the public who have found money in Jewry Street - or surrounding streets - to please hand the money into their nearest police station, as this money is evidence in our investigation.
"We would like to thank the members of the public who have already come forward and handed in money they have found to us."
The branch was forced to close while investigations were called out.