No injuries have been reported.
The Transportation Safety Board says four engines and three cars came off the tracks on Tuesday about 10 kilometres east of Slave Lake, near Mitsue.
Two of the derailed cars were carrying sulphuric chloride while one was carrying sulphuric acid.
While none of the cars carrying the hazardous material are believed to be leaking, Slave Lake fire chief Jamie Coutts says they are working to contain a small leak from one of the engines.
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