The City of Guelph says eight 170-litre drums unearthed at a construction site in the city contain solvents or a petroleum-based liquid.

The site is east of the Hanlon Expressway and north of Wellington Street, near Howitt Creek and a number of family residences.

The first two drums were discovered early Tuesday morning by a city contractor that was digging a trench for new water and sewer lines. Excavation equipment pierced through one of the metal barrels, causing it to leak a blue-green liquid.

"It had the smell of a solvent," said Majde Qaqish, the city's project engineer, who arrived on the scene shortly after the drums were unearthed.

Further excavation and a geophysical radar scan revealed six more leaking drums in the area. Qaqish said the liquid was kept in a storage tank while the city worked with the Ministry of the Environment and Climate Change to identify it.

The preliminary chemical analysis came in late Thursday morning and indicated that the drums contain solvents or petroleum-based substances. The city says it will begin proper disposal of the liquid immediately.

"We're treating the matter very carefully to ensure there's no risk to people's health and safety," Qaqish said, adding that the city is monitoring air quality as an extra precaution.