The epicenter of the tremor, which occurred at 0437 GMT, was located 111 kilometers (69 miles) south of the city Puerto El Triunfo in El Salvador, according to the USGS.

The Pacific Tsunami Warning Center said the quake took place at a depth of 54 kilometers and issued a tsunami warning for all Central American nations and Mexico, though it was not yet known if a tsunami had been generated.

No reports of casualties or damage were immediately available.

The reading was based on the open-ended Moment Magnitude scale used by US seismologists, which measures the area of the fault that ruptured and the total energy released.