Builders renovating a house in Belgium have discovered a stash of gold reportedly worth €9m (£7.6m) sealed into the walls of its cellar.

The construction workers stumbled across the hidden trove of gold bars and coins while drilling to lay new sewage pipes in the property in east Flanders earlier this week, local media report.

The discovery has sparked interest in who might get to keep the hoard – with both the builders and the local charity that owns the site having a chance of claiming it.

After launching an investigation, police warned people against attending the site to search for more treasure, saying the house was “turned upside down” and all the gold had been moved to a secure location.

The builders – including an 18-year-old working a summer job – unearthed the stash while working on the building’s foundations.

“Our first reaction was actually disbelief, amazement,” the student, named Kobe, told Belgian public broadcaster VRT.

“At first I thought they were €1 coins. But then we also saw a gold nugget lying there. That’s when we realised it was something bigger.”

Soon after, they alerted police to the discovery and explained that keeping it for themselves was not an option.

“There are so many coins and bars – it would be almost impossible,” the site manager Mario told VRT.

“Besides, that would be theft.”

Kobe agreed: “€9m – you simply can’t keep that hidden.”

The property currently belongs to CAW Oost-Vlaanderen, which provides welfare support in Dendermonde, a Flemish community of around 47,000 people.

Its director, Geert Hillaert, said his first reaction was “surprise and amazement”, adding that he hoped the treasure might eventually be used to support the charity’s work and meet the “enormous need we experience daily”.

Local police urged the public not to visit the active construction site looking for treasure.

The force – which has updated its Facebook profile picture to an image of a gold coin – said it hoped the discovery would end up in “the right place” and change people’s lives.

The rightful owner has five years to claim the hoard under Belgian law – though the local prosecutor, who has launched an investigation, said it was not yet known who this might be.

If no one comes forward, civil law states that hidden treasure on someone else’s property be divided between the finder and the property’s owner.

This only applies, though, if the stash is not found to be linked to criminal activity.

Both the builders and the charity now face a wait of up to 1,823 days for an owner to come forward. If no one speaks up to successfully claim it, silence truly will be golden.