Telephone service was disrupted over a widespread area of Southern California in the wake of Tuesday's earthquake, phone companies said, but not because of equipment damage.
The problem was that too many people were doing what both land-line and wireless phone companies normally like them to do: making calls.
"We had an 800% call spike," said Kathleen Dunleavy, spokeswoman for wireless carrier Sprint Nextel Corp.
At Verizon Wireless, the volume soared past predictions for emergencies.
"It was way above average, even for a disaster," said Ken Muche, spokesman for Verizon Wireless. "About 40% more than the peak we expect during disasters."
The volume overwhelmed telephone company equipment. Many customers reported busy signals or just silence when trying to reach family and friends. Some land lines had no dial tones.
Phone service was so disrupted that the state's Office of Emergency Services urged people to curb non-emergency calls because they could cause 911 calls to be blocked. The agency also asked people in the area not to call the emergency system simply to get general information.
In Chino Hills, near the epicenter of the 5.4 quake, phones in the sheriff's station worked only intermittently after the temblor, said Jodi Miller, spokeswoman for the San Bernardino County Sheriff's Department. The dispatch center, she said, had no disruptions.
Phone overloads are nothing new after a major occurrence, even in sports.
"That's very common after an event like this," said AT&T spokesman John Britton. "It's like what happens if the Dodgers win the World Series. Everyone picks up the cellphone and makes a call. It's called network congestion."
In some cases, people next to each other after the quake had different experiences in trying to use their phones, even when on the same network.
Sitting in a Starbucks in Pasadena, Paul Roberts was able to get calls on his cellphone. "But I am sitting here with my buddy who has AT&T, too, and he can't make outgoing calls," said Roberts, a student at Art Center College of Design.
By mid-afternoon all major land line and cellphone services said call levels were near normal and disruptions from the overload had ended.
Times staff writers Jessica Garrison and Cara Mia DiMassa contributed to this report.