Sunnyvale firefighters were able to pull a man from a burning mobile home late Wednesday, but could not save a woman as the flames engulfed the structure, authorities said.

Sunnyvale Public Safety Department Capt. Dave Verbrugge said a resident taking a walk  in the Plaza del Ray mobile home community around 11:30 p.m. spotted the fire and heard a smoke detector going off.

“He went up and knocked on the door, but couldn’t arouse the residents and then went back (home) and called 911,” he said.

Arriving firefighters found the mobile home engulfed in flames.

“They went into a rescue mode but were not able to get fully inside the house,” he said. “They were able to rescue male occupant but when they were able to knock down the fire they found a female (dead) in the rear of the residence. “

Verbrugge said it was not believed the two were related.

Neighbor Bruce Gatjen said the flames from the two-alarm fire were shooting 50 feet in the air.

“We woke up hearing the sirens,” he said. “We got curious and got up and looked out the front window…We saw flames 30-to-50 feet high.”

Verbrugge said investigators would be back on the scene Thursday trying to determine a cause of the fire.