A carbon monoxide alarm forced hundreds of guests out of their hotel rooms overnight at the Embassy Suites in Burlingame, near San Francisco International Airport.
The hotel's emergency alarms started sounding around 1 a.m. Thursday morning. Ralph Gallegos said he didn't think much of it at first.
"At first I thought someone had tripped the alarm," he said. "About 15 minutes later the police department came on and said we had to evacuate the building."
"I got out of bed thinking it was a prank and started looking around for some hoodlums so I could give 'em some grief," said Jim Heller. "Then I looked out the window and saw first responders waving their flashlights at us, so I decided to evacuate."
Between 400 and 500 people could be seen wrapped in blankets and curled up on benches outside the hotel, trying to get some sleep as emergency crews went in to test for carbon monoxide.
Investigators traced the poisonous gas to a malfunctioning boiler. Fire crews opened windows and doors in most of the hotel rooms to ventilate the building.
Most guests were allowed back into their rooms by 5 a.m.