Significant risk to bridges, river traffic and houseboat residents could be imminent as seven derelict vessels - including a retired B.C. Ferry - could break free of their moorings in Mission and float downstream.

Environment Minister Terry Lake declared an environmental emergency late Tuesday, as flood-related debris and high river flows are speculated to put "additional strain" on the vessels' moorings, which are generally in poor condition.

One of the vessels is the Queen of Sydney, B.C. Ferries' first ship in its fleet, which had been rusting in retirement on a property along the Fraser River.

It's reportedly 102 metres long, weighing in at 2,800 tonnes, and is stored beside several other vessels, including tug boats and a barge.

"The vessels also pose an environmental risk due to the potential presence of hazardous materials, physical damage to downstream habitat and risk of secondary spills from collisions with vessels or infrastructure," the ministry said in a statement.