A strong earthquake shook Mexico City and other parts of southern Mexico Tuesday morning, cracking buildings, knocking out power and sending thousands of panicked people into the streets.

At least one death was reported.Ambulances raced around the capital, sirens blaring from the 8:29 a.m. MDT tremor.

The National Earthquake Information Center in Golden, Colo., said preliminary readings indicated the quake registered 6.8 on the Richter scale.

The epicenter was 40 miles east of Acapulco, about 200 miles south of Mexico City, seismologist John Minsch said.

The tremor was felt strongly in Acapulco, causing brief power failures and panic, said Francisco Guerra, advertising director of the newspaper Novedades de Acapulco.

"I've never felt a tremor so strong in the city and I've lived here for 30 years. I thought the building would collapse," he said.

Jaime Espinosa, a fire department commander in Acapulco, said there was no serious damage in that resort city.

In Mexico City, the earthquake began as a small jolt and stopped momentarily, then buildings in the capital began swaying back and forth, with plaster cracking.

The tremor shook Mexico City at about the same time as the large earthquake that struck Sept. 19, 1985, killing at least 10,000 people and knocking down hundreds of buildings. That quake measured 8.1 on the Richter scale.

Tuesday's earthquake knocked out power and telephone service in some parts of Mexico City and damaged water lines. Schools were evacuated to check for damage.

Many buildings in the capital were evacuated.

The temblor cut off power to Televisa, the nation's largest television network, for a few minutes.

Service in Mexico City's subway stopped temporarily to check for damage on the lines.

A 19-story building that houses the Health Ministry's budget office suffered considerable damage as plaster fell, according to evacuees. The building had been rebuilt after the 1985 quake.

Carlos Bravo, who works in the penthouse offices, said, "It was horrible. There was hysteria. Parts of the ceiling fell, but they were not big enough to hurt anyone. Some of us calmed many people and made them go down the stairway."

Associated Press correspondents reported broken windows and panic in neighborhoods around the capital, including Polanco, Condesa and Napoles.

In Condesa, a resident said she heard "cracking sounds," saw "people running into the streets" and "could see the earth moving."

Radio Red reported that a police helicopter spotted no collapsed buildings.

Eduardo Almeida waited in a park outside his office in the Condesa neighborhood. "When there's an earthquake, there can be another one afterwards," he said.

An office worker who gave her name only as Magdalena, said, "It sounded like hail was falling. It sounded really ugly, as if the building was breaking."