Restart pace uneven for Canadian oil sands producers after wildfire

A massive plume of smoke, from a wildfire north of the city, stretches over Fort McMurray, Alberta, Canada Wednesday evening, May 5, 2016. Courtesy Chris Schwarz/Government of Alberta/Handout via REUTERS

WANDERING RIVER, Alberta (Reuters) - CNOOC Ltd's Nexen <0883.HK> is the latest Canadian oil sands company to warn customers it may not be able to fulfil supply contracts in the wake of a massive wildfire, as producers scramble to get facilities back online.

Nexen has issued a force majeure for all of its May production of Canadian heavy crude, two sources said on Thursday. Four major oil firms have now declared force majeure, a contract clause to remove liability for unavoidable catastrophes.