Three men were pulled out of a storm drain in Varibobi, northeast of the Greek capital, early on Thursday morning but were dead by the time rescuers got to them.
Their bodies were found by firefighters at a depth of some 8 meters. They were lying beside a small gas-operated generator, suggesting that the three men may have died of asphyxiation from its fumes.
According to investigators, the three unidentified men may have been prospecting for precious metals in the storm drain.
Police have remanded three people who were at the scene of the incident for questioning, as forensic examinations are expected to shed more light on the cause of the men’s deaths.