Two firefighters assigned to the lightning-caused Zulu Fire in the Yaak were injured Tuesday evening — one suffering from heat exhaustion, the other from a “pre-existing condition” — and flown to regional hospitals.

Both were reported in “good shape” Wednesday morning, said Forest Service Ranger Kirsten Kaiser of Three Rivers Ranger District in Troy.

The fire was reported Sunday by a lookout on Swede Mountain, Kaiser said, noting that it had probably been smoldering since the last known lightning activity more than a month ago.

The fire in the vicinity of Zulu Creek was 20 acres in size Wednesday morning, she said.

The two firefighters were among about 80 Forest Service and state Department of Natural Resources and Conservation personnel from four crews fighting the fire from the ground. In addition, “very significant air resources” — including helicopters and single-engine air tankers — attacked the fire Monday and Tuesday and remained assigned Wednesday.

A Forest Service Type III team had assumed command of the fire by Wednesday morning, spokesperson Willie Sykes said by email.

“The forecast calls for continued hot, dry weather conditions,” he wrote. “[There is] no word on containment or estimated containment date.”

Kaiser sounded confident of the progress firefighters are making.

“With four [ground] crews and all the air resources, we’re in very good shape,” she said.