People with respiratory problems were urged Tuesday to stay indoors as a large marsh fire in an isolated corner of eastern New Orleans continued to burn and spread smoke.

“The impact is potentially on 1.4 million people.” said Mayor Mitch Landrieu, who declared a state of emergency to manage the fire, which is contained in an area surrounded by water.

The Louisiana Department of Environmental Quality declared an air quality precaution day.

“Air monitors in the New Orleans area have had readings of particulate matter ranging from normal to unhealthy,” the department said. “These readings vary from location to location because of wind direction.”

Those at risk include asthma and allergy sufferers.

“We have sufficient capacity to handle visits to emergency room clinics,” said the city’s health commissioner, Karen DeSalvo.

Landrieu on Tuesday flew over the fire, which is on private property in a part of the city often called “New Orleans East.”

“The amount of smoke depends on the wind,” he said.

Landrieu met with state officials to discuss options for fighting the fire north of Chef Menteur Highway and west of Bayou Sauvage National Wildlife Refuge, but said an “aerial assault” may not help, according to CNN affiliate WWL.

The complexity of the fire and the inability to get heavy equipment to it may mean most of the acreage will have to burn itself out in coming days, the mayor told reporters. But the city and state were deploying nine helicopters to suppress the smoke and speed the process, he said.

More than 1,300 acres have burned, with an additional 1,000 acres likely to be affected. Officials said an August 24 lightning strike may have started the fire.

“The fire is in an extremely isolated area and poses no threat to citizens or property,” according to the city. “Any inconvenience or discomfort suffered from smoke is determined solely by which direction the wind blows.”