A high school in Salem shut down classes early Tuesday and an annual Downtown Trick or Treat event in Reading was canceled because of smoky conditions as firefighters continued to battle stubborn brush fires in eastern parts of the state.

School officials in Salem said there is no danger from one fire itself. Instead, the danger comes from the elevated smoke levels around the campus, the officials said. Officials also decided to relocate classes from an elementary school.

On Saturday, a woman died in an outdoor fire at an encampment in Millbury.

In Reading, about 12 miles west of Salem, town officials said Tuesday that they decided to cancel the annual trick or treat festival in the town’s business district because of concerns about air quality.

“Reports confirm multiple fires, with the largest fires burning in Salem and Middleton. Smoke from these and other fires throughout the state has led to degraded air quality, prompting concerns for the health of residents, particularly those at increased risk,” officials said in a Facebook post.

There have been dozens of brush fires reported statewide in recent days, according to the state Department of Fire Services.

Much of the state is experiencing dry to moderate drought conditions with several cities and towns — including Salem — showing unhealthy air quality, according to the Environmental Protection Agency.

In Salem, officials also warned residents Tuesday morning that there will be a National Guard helicopter operating near one of the fires to help contain the blaze. They urged people to continue to avoid the area around Salem Woods.

Officials said the fire is a different fire than a weekend brush fire near Spring Pond and that there are no structures at risk. They urged people to limit their outdoor activity in the area and to close windows to maintain indoor air quality.

National Guard helicopters have also been used to conduct water drops, including on a brush fire in the town of Middletown, about 9 miles north of Salem. according to fire officials there.

In neighboring Rhode Island, the state Department of Environmental Management issued a fire ban Monday at all state parks, campgrounds and management areas until further notice.

The ban includes campfires in designated campfire areas, including charcoal fires and cooking fires. The preventative measure applies to all Department of Environmental Management-managed lands and aims to reduce the threat of human-caused wildfires, officials said.