The fire began Tuesday night and has since burned 200 acres--about a fifth of the preserve. Several vacation homes are in the path of the flames.
Crews with the state forest service and the Nature Conservancy are trying to contain the flames by digging fire lines, and by burning portions of land in the fire's path to reduce fuel.
Nature Conservancy spokeswoman Debbie Crane said Thursday, gusty conditions aren't helping crews' efforts.
"We're a little concerned this afternoon the wind is supposed to pick up a little bit," she said. "And that's what we've been fighting the whole time since this fire was reported."
Crane said firefighters thought they had the fire contained a few hours after the fire was reported late Tuesday.
"Then the wind started picking up, and the humidity dropped," Crane said, "and that's when it was not contained any more."
Crane said authorities don't know how the wildfire started. She said there have been no lightning strikes, no house fires, and that campfires are not allow in the park.
"Certainly arson is one thing that everybody will be looking into, since you don't have any other reason to assume a fire started there," she said.