WASHINGTON - A strong quake of magnitude 6.5 struck north off Puerto Rico on Monday and could trigger a local tsunami, the US Geological Survey (USGS) said.
It said the quake, initially reported as a magnitude 6.4, was very shallow, at a depth of 17.7 miles (27 km) below the seabed. It struck at 12:01 a.m. (0401 GMT), 35 miles (56 km) north of the town of Hatillo.
The Pacific Tsunami Warning Center said the quake could trigger a local tsunami.
"There is the small possibility of a local tsunami that could affect coasts located usually no more than a hundred kilometers (63 miles) from the earthquake epicenter," the tsunami centre said in its advisory.
There were no immediate reports of damage.
Sunday marked the fourth anniversary of the devastating 7.0 magnitude earthquake in nearby Haiti that killed more than 200,000 people and left 1.5 million homeless.