Hurricane Earl is gaining strength as it brought heavy winds and rain to Puerto Rico and the Virgin Islands on Monday.

Forecasters at the National Hurricane Center say Earl intensified into a Category 4 storm late Monday as it moved into the Caribbean region.

Warm water temperatures and calm upper winds are creating conditions for Earl to strengthen even more on Tuesday.

Forecaster Todd Kimberlain says the storm is beginning to turn northwest on a path that will take it away from land.

"The high sustained winds are now 135 mph [217.26 kph] with higher gusts.  There is some potential for Earl to strengthen a bit more," said Kimberlain.  "The good news is that, on our forecast track, the center of Earl will be moving away from the U.S. Virgin Islands and Puerto Rico tonight.  And on the forecast track, we are forecasting it to pass east of the Turks and Caicos islands on Tuesday."

Earlier, heavy rains caused flooding in low-lying areas of Antigua, and winds ripped out trees and blew down power lines on the nearby island of St. Martin.

U.S. Coast Guard officials on Monday suspended all traffic in and out of ports in the U.S. Virgin Islands and eastern parts of Puerto Rico because of strong winds.

The forecast shows Earl will not hit Florida or other southern U.S. states in coming days.  But forecaster Kimberlain says it is too early to tell whether states from North Carolina to Maine are at risk.

"At this point, our forecast track does keep it offshore, but it's probably going to get uncomfortably close, enough so that people are going to have to pay very close attention to this," he said.  "Depending on how it plays out, there is the potential for watches and warnings."

Forecasters say another tropical storm, Fiona, has formed in the Atlantic Ocean, and is moving on a path similar to Earl's.  Experts say Fiona might gain strength and begin to affect eastern parts of the Caribbean by late Tuesday.