Tenants with one spare bedroom have had a payment reduction of 14% and those deemed to have two or more spare a reduction of 25%.
Lawyers for the 11 cases say that, unless the families move from their homes into smaller properties, they face building up rent arrears and being forced out any way.
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A manhunt is being undertaken after two men were shot - one fatally - at a residential site on Thursday evening.
Residents of Fort McMurray were restricted to salvaging only their clothes and pets as they were evacuated.
Warm sunshine to end the working week