Miami, Florida (CNN) -- The death toll attributed to Hurricane Tomas, which swept through the West Indies island of St. Lucia last weekend, rose Tuesday to 12 and Prime Minister Stephenson King issued a declaration of disaster.
"No one could have adequately prepared for the event as the hurricane moved very slowly, a mere 8 miles per hour over the country, and deposited two years' annual rainfall in a 24-hour period," said June Soomer, an official in the prime minister's office.
Tomas hit St. Lucia as a Category 1 hurricane on Sunday morning and caused major damage by the time its winds subsided Monday night.
"Roads and bridges have collapsed, schools damaged ... homes have been destroyed," Soomer said. Some towns, including the town of Soufriere on the southwest coast, were reachable only by sea, she said.
But two bridges in the north have been partially reopened so people can get from the fishing village of Gros-Islet to the capital city, Castries, she said.
Hewanorra International Airport has reopened.
Aid from the United States and France was expected to arrive Tuesday to help clear roads, she said.
But access to fresh water remained a concern: Soomer predicted damaged water mains would be "at least halfway back to normal" by the end of the week.
Tomas also caused damage on St. Vincent, where two people were injured when they attempted to fix roof damage during the storm, officials said. The storm sent some 1,000 people into shelters, said Michelle Forbes, acting director of National Emergency Management.
Meanwhile, Jamaica's government issued a hurricane watch for the island late Tuesday afternoon as Tomas continued its trek through the region. After striking the Windward Islands, which include St. Lucia, Tomas emerged into the Caribbean Sea and weakened into a tropical storm. However, it was expected to reintensify and take a sharp right turn, forecasters said Tuesday.
People in Haiti and the Dominican Republic were urged to monitor the progress of Tomas, which could pose a "significant threat" to those areas later in the week, the National Hurricane Center said.
With the possibility of landslides, flooding and washed-out roads and bridges if Haiti is hit by the Tomas, the United Nations was scrambling to get supplies to key staging areas on the island, a U.N. spokesman said Tuesday.
"Supplies are being pre-positioned notably in Jeremie, Les Cayes, Jacmel and Leogane which are expected to experience the storm more severely," according to Martin Nesirky with the U.N. Office for the Coordination of Humanitarian Affairs.
The official forecast track from the Miami, Florida-based National Hurricane Center shows Tomas making landfall in southwestern Haiti on Friday afternoon as a Category 1 hurricane, with sustained winds of at least 74 mph with higher gusts.
As of 11 p.m. ET, Tomas was carrying 40 mph (65 kph) winds and was centered and 385 miles (620 kilometers) south-southwest of Port au Prince, Haiti and about 320 miles (515 kilometers) south-southeast of Kingston, Jamaica, the center said.
It was moving west at 8 mph (13 kph) and was expected to slow and turn to the north over the next two days.
It could regain hurricane strength by Thursday, the center said.
November hurricanes are rare, said CNN meteorologist Bonnie Schneider. The Atlantic hurricane season ends November 30.
CNN's Mark Bixler and CNN Radio's Matt Cherry contributed to this report.