The California Office of Emergency Services has urged people throughout Southern California to cut back telephone use in the aftermath of Tuesday's earthquake.

Phone lines have been jammed because of the volume of calls from people checking on their friends and relatives, California Office of Emergency Services spokesman Kelly Huston said.

"The big message now is don't use telephones or cell phones in Southern California," Huston said. "The systems down there are maxed out, and that creates a really dangerous situation when it comes to people who need to call 911 for an emergency."

Some people apparently are dialing 911 for general information about the 5.4-magnitude quake. Huston said people should not do that.

The urgent request from state emergency officials applies to both cell phones and landline phones.

Bill Kula, a spokesman for Verizon Communications Inc., said the company received sporadic reports of outages for landline phone service in and around Pomona, which is near the epicenter. But he said there was no effect on wireless service.

AT&T Inc. spokesman Fletcher Cook said he had received no damage reports.

Both companies provide local phone service in areas affected by the quake.