EVERETT, Wash. -- Firefighters in Snohomish County continue to battle a stubborn fire on Jetty Island off the Everett waterfront.

The fire began on the first day of Jetty Island Days, in which the island was opened to visitors.

The fire lit up the night sky in red Wednesday as flames spread through brush that was 8 feet tall.

The flames had mostly died down by Thursday morning, but firefighters will work throughout the day to make sure the fire is out.

Firefighters are taking boats to the Island to battle it by hand using portable pumps. A sheriff's helicopter also poured water onto the fire.

Crews are trying to keep the blaze from burning Coast Guard navigation equipment on the island.

A pyrotechnics crew across the water from the island was among the first to see the flames and call 911, police said. The crew is setting up a fireworks show for Everett's Fourth of July celebration on Saturday.

The fire has raised concerns about shooting off fireworks so close to an area that could easily burn.

Ferry service to the area will resume at 10 a.m.

The cause of the fire is not yet known.