NEW YORK: Authorities charged a teenager with aggravated arson, prosecutors said Thursday, after a forest fire scorched 15,000 acres of land in New Jersey, in the northeastern United States, forcing thousands of people to flee their homes.

The fires spreading in Ocean County, the coastal region of New Jersey, south of New York, are only half contained, according to the latest update from firefighters posted on Facebook.

The fire, which has so far destroyed a commercial building, could become the largest in New Jersey for 20 years.

Prosecutors said that on Wednesday they charged a 19-year-old man from the region with aggravated arson following what they allege was an improperly extinguished bonfire.

Since Tuesday, images have shown thick smoke in the sky above the region.

New York health authorities warned Thursday morning that air quality would be degraded, recommending vulnerable communities limit their outdoor activities.

The blaze erupted in the pine forests of New Jersey, one of the largest protected areas on the East Coast. The state was put under drought alert in March. - AFP