WHITE SWAN, Wash. — After about four hours Sunday, approximately 90 firefighters contained a fire that burned a stretch of sagebrush, cottonwoods and a few outbuildings.

The flat, sparsely populated area was smoldering late Sunday evening as firefighters — some in helicopters — from across the region put out the dying flames.

The cause of the fire, which began about 2:30 p.m., is unknown and remains under investigation.

Initial fears that the fire may have burned some homes proved erroneous, although a wooden bridge on Ransier Road was destroyed. No injuries were reported.

Throughout the afternoon, three helicopters repeatedly dumped 500-gallon loads of water from nearby ponds onto the flames. Meanwhile, a small air-attack plane controlled the air space.

By about 7:30 p.m., many of the nearly 30 fire units had already left and the cloud of smoke that hung over the fields was dissipating.

But Yakima Fire District No. 5 Capt. Dave Martin said there was still much work to be done.

“We have this contained but by no means controlled,” he said. “We’ll have people out here fairly late tonight and for a couple more days, in case there’s a wind shift. If the wind blows the smoldering embers, it will take off and keep going.”

The fire started along Signal Peak Road, south of the unincorporated community of White Swan.

Firefighters from stations across the Lower Valley were called out to help fight flames. The Department of Natural Resources and U.S. Forest Service provided air support.

Battling the fire was made difficult by dense stands of old, tall sagebrush and cottonwoods, firefighters said.

• Melissa Sánchez can be reached at 509-577-7675 or msanchez@yakimaherald.com.