A 5.5 magnitude earthquake hit Mexico City on Tuesday, causing buildings to sway and thousands of people to run into the streets.

Mexico is one of the most seismologically active regions in the world. In 1985 Mexico was rocked with an 8.1 magnitude earthquake, which killed 9,500 people.

There were no immediate reports of death or damage in the most recent Mexico City earthquake. On Monday, a 6.2 magnitude struck Guatemala City, but residents there did not feel Tuesday's Mexico City earthquake.

The Mexico City earthquake struck the city at 7:04 am. According to the US Geological survey the earthquake centered about 10 miles southwest of Pinotepa Nacional on the Pacific Coast and 227 miles southeast of Mexico City.

The Mayor of Mexico City, Manuel Mancera, used his twitter account to let people know there was no damage to any of the buildings. The people of Mexico City were scared when the alarm sounded telling them to evacuate the tall buildings. Another earthquake struck a few minutes later, sounding the alarm again.

Earthquake.usgs.gov says an earthquake is caused when "two blocks of the earth suddenly slip past one another." Most earthquakes happen along the edge of the ocean and continental plates. They can also occur along fault lines, which are cracks in the Earth where plates move passed one another.