Crews searched a Del Mar Heights canyon for a person after someone reported hearing screams for help Thursday night.
After hours of looking using helicopters with infrared cameras and search teams with night vision goggles, officials called off the search around 11:30 p.m.
Residents called 911 around 9 p.m. saying they could hear a man screaming in the canyon.
"It sounded like screaming," said Sam Hiraoka. "I couldn't make out any words."
At about 10:45 p.m. San Diego police officers asked television live truck operators and a fire engine crew to shut off their vehicles so an officer could call out to the man using a megaphone.
No response was heard.
Search crews planned to be back out at dawn with search and rescue dogs to look again.