HONOLULU (AP) — A wildfire in Hawaii’s Central Oahu has grown to cover more than a square mile (2.5 square kilometers) in a remote mountainous area and has burned native koa and ohia trees, officials said Tuesday. No structures or homes were threatened and no evacuations were ordered.

Multiple helicopters from the Honolulu Fire Department, the U.S. Army and the state dropped buckets of water on the blaze from the air for a second straight day.

Mililani and Wahiawa are the towns closest to the flames, but they weren’t at risk. Army installations Schofield Barracks and Wheeler Army Airfield are also in the area, which is about about 20 miles (32 kilometers) north of Honolulu.

Video footage shot by the state Department of Land and Natural Resources showed white and brown smoke rising from green forests. Black and grey patches covered already scorched hillsides.

Firefighters battled flames from the air because the terrain is rough and inaccessible. The fire was moving east on a ridge and was 30% contained by midafternoon Tuesday, the Honolulu Fire Department said in a news release.

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The fire burned through heavy timber and native vegetation, the state said.

Hawaii’s tropical forests evolved without experiencing frequent fires and flames aren’t a part of their natural life cycle.

Invasive plants often grow on burned lands, which increases the risk of future wildfires, according to a 2013 state action plan for koa forests. The report said climate change was expected to worsen Hawaii’s wildfire problem.

Oahu is currently going through a dry spell even though the winter rainy season began in October. The U.S. Drought Monitor said Central Oahu was in moderate drought as of last week.

In August, multiple wildfires erupted on Maui including a blaze that killed at least 99 people and destroyed more than 2,000 structures in Lahaina. Powerful winds related to a hurricane passing far to Hawaii’s south helped fuel that fire and prevented firefighters from using helicopters to tackle the flames.