VANCOUVER -- Health officials have declared a COVID-19 outbreak at two sites along the route of a natural gas pipeline under construction in B.C.'s north.

Northern Health announced Sunday that it had found "evidence of COVID-19 transmission" among workers housed at the 7 Mile Lodge and Little Rock Lake Lodge accommodation sites along the Coastal GasLink pipeline route.

In a news release, the health authority said 27 employees working for the contractor Pacific Atlantic Pipeline Construction had tested positive for the coronavirus, adding that they had been working at and moving between the two sites.

Of the 27 cases, 17 remain active, Northern Health said.

Workers who have tested positive and their close contacts have been instructed to self-isolate, either at their current locations, in alternate accommodations, or in their home communities, according to the health authority.

In addition to declaring the outbreak, health officials have "issued an order that these worksites be limited to all but essential workers, until public health approves an updated COVID-19 safety plan," Northern Health said.

The outbreak declaration will be in place for at least 28 days, according to Northern Health.

Coastal GasLink is not the only liquefied natural gas project in northern B.C. to face a COVID-19 outbreak this month.

An outbreak was declared last week at an LNG Canada project site in Kitimat, and is the second outbreak of the disease at an LNG Canada site.