The siren, located at Regatta Boulevard and South 32nd Street, began sounding at about 7:10 a.m.
Katherine Hern, the county's community warning system manager, said a crew was sent to investigate the problem, and the siren has since been deactivated.
The siren is one of 17 in Richmond and 42 throughout the county, she said.
Hern said that when the siren sounded, emergency dispatchers were inundated with phone calls.
"When things like this do happen, the first thing people should do is turn on the radio, turn on the TV and stay off the phone because if there had been an emergency we would have been trying to call them to tell them what happened," Hern said.
She said that if there had been a hazard, residents would have received an automated phone call instructing them on what to do.
An employee at the nearby Richmond Wholesale Meat Co. said she was among those who called 911 to find out what was going on. She said she thought it might be a problem at the Chevron refinery.
The 911 dispatcher told her it was a false alarm.
"They told me before I even asked, so I guess they got a lot of calls," said the employee, who didn't want to be named.
She said the siren was sounding for about half an hour.
Workers at Grace Baking Co. on Regatta Boulevard didn't hear a thing and weren't aware that a siren had gone off, an employee there said. She explained that there is a lot of noise from the machinery in the bakery.
Hern apologized to those in the area who were bothered or frightened by the siren.
"Overall we're very sorry for the inconvenience," she said. "We do have mechanical glitches from time to time."
The cause of the malfunction hasn't yet been determined.