A magnitude-5.1 earthquake centered southeast of downtown Los Angeles left little in the way of damage but made many people nervous because of the approximately 40 aftershocks.

The U.S. Geological Survey said the largest temblor struck at 9:09 p.m. Friday, with its epicenter between the towns of La Habra and Brea in Orange County and at a depth of 7.5 kilometers (4 3/4 miles).

The USGS continues recording the quake's aftershocks, which had reached 38 by the time of its last report.

"The aftershock sequence may continue for several days to weeks, but will likely decay in frequency and magnitude as time goes by," the USGS said.

Despite the continuing aftershocks, the Los Angeles Fire Department said there is no longer an earthquake alert and that only minor damage has been observed.

The Fire Department did not receive any immediate reports of damage following an initial assessment by firefighters from its 106 stations, the department's Erik Scott said.

Local authorities said on their Twitter accounts that the temblor caused broken window panes and cracked pipes with gas and water leakage.

The electricity company Southern California Edison said that some 2,000 customers suffered blackouts because of the temblor.

Authorities said they have given instructions to check bridges, dams, railroads and other infrastructure for possible damage.

Residents of the affected area said in a statement on local radio station KNX-AM that they had seen a brick wall collapse and trees and electric powerlines that looked like they were about to come crashing down.

Tom Connolly, who lives in La Mirada near La Habra, said the magnitude-5.1 quake lasted about 30 seconds.

"We felt a really good jolt. It was a long rumble and it just didn't feel like it would end," he told the Associated Press. "Right in the beginning it shook really hard, so it was a little unnerving. People got quiet and started bracing themselves by holding on to each other. It was a little scary."

The quake also caused the closure of the Metrolink railroad line for an inspection of its tracks and trains.

Seismologists believe there is a 98-percent probability that a "Big One," an earthquake of or above a magnitude-7.8 originating in the San Andres Fault, will affect Southern California in the next 30 years. EFE