A 6.6 magnitude earthquake struck off the coast of El Salvador on Thursday near the capital but authorities said there were no initial reports of casualties or damage.
The quake was so strong it was likely felt throughout Central America, officials said.
The U.S. Geological Survey reported the quake had a preliminary magnitude of 6.6. Its epicenter was about 17 miles (28 kilometers) south-southeast of La Libertad, a suburb of the regional capital, Santa Tecla, and it was recorded at a depth of 65 kilometers (40 miles).
The Salvadoran environment ministry said the quake was even stronger, with a magnitude of 6.8.
The Pacific Tsunami Warning Center did not issue an alert for the quake but the Salvadoran environment ministry issued its own tsunami warning, predicting sea level variations of up to 12 inches.
However, Environment Minister Lina Pohl said the alert was sent "as a protocol."
Coastal residents should avoid entering the water for four hours after the quake, the ministry said on Twitter.
President-elect Nayib Bukele, who takes office on Saturday, said on Twitter that the earthquake was felt "throughout 100% of the country."
Police and firemen fanned out across the country to evaluate the situation and reported "no serious or generalized damage," the Civil Protection department said on Twitter.
The Education Ministry canceled classes in coastal areas.
In the coastal town of Puerto de la Libertad, authorities evacuated families who live near the water.
Rattled residents stood outside their homes Thursday morning digesting the quake.
"The quake was very strong. Thank God, nothing happened to me. But we are taking precautions," one of them, Maria Valencia, told Canal 21 television.
The Environment Ministry reported as many as 12 aftershocks ranging from 3.3 to 4.9 in magnitude.
In San Salvador, police and soldiers patrolled streets but people largely stayed indoors despite the scare from the quake.
The government gave slightly different figures for its location.
It placed it more shallow than the USGS at 48 kilometers, and said the epicenter was a bit further out to sea, some 66 kilometers from Puerto de La Libertad.
