A magnitude 5.9 earthquake shook the southern Mexican state of Oaxaca on Monday, days after a more powerful temblor hit the same area.
State and national emergency officials said they had no immediate reports of damage from the latest shake, but schools were cancelled across the state on Monday.
It was felt in Mexico City, where quake alarm sirens had people springing out of their beds and into the streets.
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The U.S. Geological Survey said the quake hit at 12:57 a.m. (0657 GMT). It was centered 25 miles (40 kilometers) beneath the surface at a point 33 miles (54 kilometers) east-northeast of Pinotepa Nacional and 69 miles (111 kilometers) southwest of the state capital, Oaxaca city.
It appeared to be an aftershock of a magnitude 7.2 earthquake that struck near the same area on Friday. That quake caused no deaths, though 13 people were killed in the crash of a helicopter sent to assess the damage.