A Belgian student who was excavating trenches for a sewage system has discovered a trove of gold worth an estimated €9 million ($14.7 million).

The 18-year-old, named Kobe, was among a group of builders renovating a house on the site of a former brewery in Sint-Gillis-Dendermonde, about 30km north-west of Brussels.

He told the Belgian news network VTM that at first, they thought they’d found €1 coins so began digging them up. Then they saw a gold bar. “It turned out to be a bit more than we thought.”

Site manager Mario told VTM, “They shouted: ‘We’ve found gold!’ I went to have a look and picked up the gold. We kept digging up more coins and bars. Only then did it really sink in what we’d found. It was a strange feeling.”

The hoard was stashed in a bag in a bricked-in cellar wall. Photo: Dendermonde Police

The hoard, which includes gold coins, nuggets and numbered bullion bars, was stashed in a bag in a bricked-in cellar wall beneath the grand villa occupied by the brewery’s owner, Theophilus Van Assche, in the late 19th century. Kobe said it appeared to have been deliberately hidden.

Under Belgian law, the rightful owner has five years to claim the hoard but it is not yet clear who that might be. The builders, the welfare organisation that owns the building and any descendants of the Van Assche family could all have a claim to the fortune.

Police have warned people against coming to the site to search for more treasure, saying all of the gold has been moved to a secure location.

Brewing on the site began in 1899 and continued until 1970. The property is being renovated to create new offices and housing.

The builders first thought they had discovered €1 coins. Photo: Dendermonde Police

The builders called the police as soon as they came across the treasure. Police have launched an investigation to establish its legal ownership. Authorities must verify that it was not stolen property or the proceeds of criminal activity.

Kobe told VTM the builders knew they would have to hand it over to authorities. “If it had been a few coins, maybe not,” he said. “But maybe we’ll get some kind of finder’s reward eventually.

“It’s just not something you expect when you’re working on a regular Tuesday morning.”