A fire Saturday night at the Hills Mobile Home Park on Skyline Drive in Richland destroyed one home and heavily damaged another, authorities said.
Two vehicles also were burned.
The blaze broke out around 10 p.m.
A passerby walking a dog spotted flames and alerted the couple sleeping inside, said Richland fire Battalion Chief Brenda Rodgers. The couple got out safely.
The fire spread to the second home, two vehicles and some nearby wildland, authorities said.
No residents were hurt. One Richland firefighter sustained a minor burn.
The cause has not yet been determined, and authorities continue to investigate.
Crews from Kennewick Fire Department and Benton Fire Districts 1 and 4 helped Richland with the blaze.