A lottery ticket seller hailed as a good samaritan 11 years ago for apparently trying to track down the owner of an unclaimed winning ticket worth €4.7m (£4.05m) faces a possible six-year jail sentence on charges that he defrauded the rightful owner of their winnings.

Police allege that Manuel Reija González, a ticket seller in the north-western Spanish city of A Coruña, told the winner of the lottery drawn in June 2012 that his ticket was worth just over a euro and then, with the help of his brother, who worked for the national lottery, attempted to cash in the ticket himself. Both brothers have denied any wrongdoing.

The unclaimed ticket was national news at the time and Reija was praised when he told media that after finding the ticket, he was trying to track down the winner rather than claim the money for himself.

However, lottery authorities became suspicious of Reija’s version of events and an investigation was launched. The local authority instigated a search for lost property to find the rightful owner of the winning ticket. A total of 317 people from all over Spain claimed they were the winner but all of the claims proved false.

A judge ordered police to investigate Reija for possible fraud but the investigators, led by chief inspector José Manuel López, were also determined to track down the legitimate winner.

There are various lotteries in Spain. The lottery in question, which is held twice a week is known as la primitiva. For a small, stake punters select six numbers out of a possible 49. If there isn’t a winner, the lottery is rolled over until the next draw.

The police discovered someone in A Coruña had been using the same combination of numbers over a long period of time. An identical combination cropped up at lottery offices in holiday destinations on the Costa del Sol and in Mallorca.

“We reached the conclusion that this was someone with plenty of free time who took the Christmas and Easter holidays somewhere warm, probably a pensioner,” López said.

Through Imserso, a state body that organises holidays for elderly people, police tracked down a woman whose movements corresponded with the ticket sales. It emerged that she was the wife of the ticket’s buyer, who had died in 2014.