Photo by Mike Licht and courtesy of Creative Commons.

According to Reuters:

The U.S. Geological Survey said the quake was magnitude 6.3 and centered close to Ometepec in the southwestern state of Guerrero, where a much more powerful earthquake struck last month. It was measured at a depth of 6.2 miles, the survey said.

So far the earthquake does not seem to have caused severe damage in Mexico City.

The earthquake was likely an aftershock of the 7.4 earthquake that hit the region on March 20.