The quake struck off the southern coast of the U.S. territory in the Caribbean Sea at a shallow depth of 6 kilometers, or under 4 miles. The epicenter was recorded just 8 miles south of Indios, Puerto Rico, according to the U.S. Geological Survey.
It's the latest in a string of earthquakes to hit the island's southern region over the past several days.
Angel Vazquez, the emergency management director for the city of Ponce, 17 miles east of Indios, told The Associated Press that the shaking from Monday's quake "lasted a long time."
"This is one of the strongest quakes to date since it started shaking on Dec. 28," he said.