NEW ORLEANS (AP) — Louisiana Department of Agriculture and Forestry spokesman Sam Irwin says an aerial survey indicates that a big marsh fire in the New Orleans area could burn out on the surface by Wednesday afternoon, although it could continue to burn underground.

Easterly winds kept a pall of smoke from the fire over the New Orleans area for the third straight day Tuesday. The National Weather Service issued a smoke alert for seven parishes. Meteorologists said the smoke could move north — mostly over Lake Pontchartrain — by evening.

The fire is on 2,300 acres surrounded by canals. Irwin said Tuesday’s survey showed that just over three square miles have burned. That leaves just over one-half-square mile to burn. It is unclear how long the fire might burn beneath the surface.