Update: At about 7 p.m. PDT,  Mexican authorities were putting the human death toll from Tuesday’s earthquake at 139. The number is expected to increase.

MEXICO CITY — A powerful earthquake jolted central Mexico on Tuesday, cracking building facades and scattering rubble on streets in the capital on the anniversary of a devastating 1985 quake.

The quake caused buildings to sway sickeningly in Mexico City and sent panicked office workers streaming into the streets, but the full extent of the damage was not yet clear.

The U.S. Geological Survey said the quake had a magnitude of 7.1 and was centered near the Puebla state town of Raboso, about 76 miles (123 kilometers) southeast of Mexico City.

Thousands of people fled office buildings and hugged to calm each other along Mexico City’s central Reforma Avenue as alarms blared, and traffic stopped around the Angel of Independence monument.

In the Roma neighborhood, which was struck hard by the 1985 quake, piles of stucco and brick fallen from building facades littered the streets. Two men calmed a woman seated on a stool in the street, blood trickling form a small wound on her knee.

At a nearby market, a worker in a hardhat walked around the outside warning people not to smoke as a smell of gas filled the air.

Market stall vendor Edith Lopez, 25, said she was in a taxi a few blocks away when the quake struck. She said she saw glass bursting out of the windows of some buildings. She was anxiously trying to locate her children, whom she had left in the care of her disabled mother.

Pictures fell from office building walls, objects were shaken off of flat surfaces and computer monitors toppled over. Some people dove for cover under desks. Local media broadcast video of whitecap waves churning the city’s normally placid canals of Xochimilco as boats bobbed up and down.

Earlier in the day workplaces across the city held preparation drills on the anniversary of the 1985 quake, a magnitude 8.1 shake, which killed thousands of people and devastated large parts of Mexico City.

Much of Mexico City is built on former lakebed, and the soil is known to amplify the effects of earthquakes even hundreds of miles away.