Tropical storm Tomas is gaining strength as it approaches Haiti, where a hurricane warning is in effect.

The Haitian government has urged the people forced into camps and tent cities after January's devastating earthquake to seek shelter with friends and families.

"We are using radio stations to announce to people that if they don't have a place to go, but they have friends and families, they should move into a place that is secure," said civil protection official Nadia Lochard, who oversees the department that includes the capital, Port-au-Prince.

The news of Tomas's predicted pass slowly filtered through Port-au-Prince via wind-up radios and megaphone announcements, unease set in among people who already lost homes and loved ones in the quake and saw their tents ripped apart in lesser storms this year.

Tomas was upgraded back to tropical storm status Wednesday evening, the U.S. National Hurricane Center said. By Thursday morning, the storm had maximum sustained winds of 85 km/h, with some strengthening expected.

"The forecast track this morning takes Tomas across the western edge of Haiti as a Category 1 hurricane tomorrow morning," CBC meteorologist Johanna Wagstaffe said.