Around 30 metric tons of diesel fuel spilled into the Yenisei River in Siberia after a ship towing two barges ran aground and broke apart in shallow water, Russian authorities said Monday.

Investigators said the ship struck an underwater obstacle, causing the barges to detach and pierce the hull of the vessel, which began leaking fuel around 6 p.m. local time Sunday.

The Yenisei River, which begins in northern Mongolia and empties into the Arctic Ocean, stretches 3,487 kilometers (2,167 miles), making it the fifth longest river system in the world.

Prosecutors said the spill stretched up to 50 kilometers (31 miles) along the shoreline and that they were overseeing containment efforts. The ship’s owner was identified as the Tyumen-based Ob-Irtysh River Shipping Company.

The Krasnoyarsk branch of Russia’s Emergency Situations Ministry said the crew managed to prevent the barges from drifting further down the river.