Residents of Blackhall Colliery have been stumbling across wads of £20 notes – usually worth £2,000 – in the former mining village in County Durham.
The latest discovery was on Monday, meaning four of these cash bundles have been handed in this year and 13 since 2014.
The wads are usually left in plain sight and have been scattered across the small coastal village.
The owner has two weeks to collect the cash, which is then returned to the finder if not claimed, according to Peterlee Police.
A Durham Police spokesperson said the money has been returned to the lucky finders in all cases bar yesterday.
Detective Constable John Forster said in a statement: “The circumstances remain a mystery so we would welcome any information that will help us get to the bottom of these random incidents.”
He said they have conducted fingerprint tests, checked with local banks and conducted numerous interviews, but the case still remains unsolved.
“This could be the work of a Good Samaritan,” DC Forster said. “We would like to thank the residents who have shown incredible community spirit by handing the money in.”
He told The Northern Echo: “It isn’t an affluent part of the world, so for them to find cash and that amount to instantly think about taking it to the police stations shows the community spirit there is.
“I have looked into it and I am not thinking crime, drug dealing or money laundering. Drug dealers are not known for being reckless with their money.”