U.S. Southern Command sent an assessment team and three CH-47 Chinook helicopters to Grand Cayman on Thursday to pre-position for the U.S. interagency disaster relief response for Jamaica in the wake of Hurricane Melissa.

This military assessment team is separate from the Disaster Assistance Response Team sent by the State Department. The military assessment team will make its own assessment and what U.S. military assets and capabilities might be needed to provide assistance to Jamaica.

-ABC News' Luis Martinez

Over 170 communities in the six most severely impacted parishes of Jamaica have been moderately or severely affected by flooding, Minister of Local Government and Community Development Desmond McKenzie said.

About 13,000 people are staying in 521 shelters as of Thursday afternoon, he said.

“The numbers in the shelters have been reduced substantially over the past day because many persons who went to the shelter out of precaution have left those facilities and gone back home,” McKenzie said.

Search and rescue efforts are ongoing, and emergency services are making arrangements to get food and water into Black River, one of the hardest-hit communities, he said.

-ABC News’ Ellie Kaufman

The death toll across Jamaica is expected to rise, but Minister of Local Government and Community Development Desmond McKenzie would not provide a number on Thursday.

"There has been casualties, and we do anticipate, based on our information, that they'll be more," McKenzie said at a news conference.

About 13,000 people remain in shelters across the island, McKenzie said.

-ABC News’ Othon Leyva

More than 490,000 customers are without power in Jamaica, accounting for 72% of customers, according to Minister of Science, Energy, Telecommunications and Transport Daryl Vaz.

Several parishes, including St. Elizabeth, Westmoreland and Hanover are completely without power, Vaz said

The Jamaica Defence Force is cutting its way to areas in the western parts of the island by foot, officials said.

The JDF is also working to airlift patients out of hard-hit areas.

Officials said clearing roadways has been very difficult with trees, mud and up to 4 feet of sand blocking roads across the island.

-ABC News’ Othon Leyva

As Jamaica braces for the impact of Hurricane Melissa, Jamaica’s minister of Labour and Social Security, Pearnel Charles Jr., joined ABC News Live, saying those in especially vulnerable areas need to heed the warnings of officials.

"The Prime Minister has also declared evacuation orders, which means it's not a suggestion; it is a directive to save your life, to remove yourself from communities that are extremely vulnerable, the low-lying, flood-prone areas, and to get you to a shelter," Charles said.

The evacuation Order applies to Port Royal in Kingston; Portland Cottage and Rocky Point in Clarendon; Old Harbour Bay in St. Catherine; and New Haven, Riverton City and Taylor Land in St. Andrew, according to officials.

"Don't wait, don't gamble with your life if you are in one of those areas that are low lying, just get out, you know, secure what you can secure. ... Get your medicine, get your documents, get your children and get to a space that is higher ground and safer," Charles added.

"There is no possession or pride that is as important as a single life. So the message is, protect yourself, protect your family, and also look out for the elders. Look out for the persons with disabilities and those right now who need support. It's unity and collaboration to protect this nation," he said.