A construction crane spilled around 230l of diesel into a river near the Alaskan city of Fairbanks when it tipped over while working on a project to build a bridge.
The state transport department said work is being carried out to try to contain the spillage.
A department spokesman said environmental officials are on-hand and have placed a protective curtain along the site area, lining the banks of the river. More booms were put downriver too, she said.
The crane operator is in hospital for checks but no one has been injured.
A local newspaper reported witnesses hearing the crane crash onto its side. Working at a nearby church, Joe Fields said: “I heard something loud and I thought maybe they dropped a pipe. It took me two or three minutes but then I realised that the crane wasn’t there any more.”
The state spokeswoman said the crane base was on the north side of the river and tipped over to extend across the water, with its tip landing on the other side. The crane had apparently over-reached while pile-driving a pillar about 12m away from it.