SAN JUAN, Puerto Rico (AP) — Erin strengthened into a hurricane on Friday as it approached the northeast Caribbean, prompting forecasters to warn of possible flooding and landslides.

The storm is expected to remain over open waters, although tropical storm watches were issued for Anguilla, Barbuda, St. Martin, St. Barts, Saba, St. Eustatius and St. Maarten.

Heavy rains were forecast to start late Friday in Antigua and Barbuda, the U.S. and British Virgin Islands and southern and eastern Puerto Rico. Up to 4 inches are expected, with isolated totals of up to 6 inches, according to the National Hurricane Center in Miami.

The hurricane center also warned of dangerous swells but said the threat of direct impacts in the Bahamas and along the east coast of the United States “appears to be gradually decreasing.”

Hurricane specialist and storm surge expert Michael Lowry said Erin is forecast to eventually take a sharp turn northeast that would put it on a path between the U.S. and Bermuda.

The U.S. government has deployed more than 200 employees from the Federal Emergency Management Agency and other agencies to Puerto Rico as a precaution as forecasters issued a flood watch for the entire U.S. territory from late Friday into Monday.

Puerto Rico Housing Secretary Ciary Pérez Peña said 367 shelters have been inspected and could be opened if needed.

The U.S. Coast Guard said Friday that it closed six seaports in Puerto Rico and two in the U.S. Virgin Islands to all incoming vessels unless they had received prior authorization.

Meanwhile, officials in the Bahamas said they prepared some public shelters as a precaution as they urged people to track the hurricane.

“These storms are very volatile and can make sudden shifts in movement,” said Aarone Sargent, managing director for the Bahamas’ disaster risk management authority.