What you need to know about the federal response to the crisis in Puerto Rico

— -- President Donald Trump will make his first visit to Puerto Rico next Tuesday as the island struggles to recover from Hurricane Maria.

The strongest storm to make landfall in Puerto Rico in nearly 90 years, Maria killed at least 16 people and left most of the island's 3.4 million people without power.

Officials said half the island's population remains without water and communications systems are still down a week after Maria moved through.

"What's out there is total devastation. Total annihilation," San Juan Mayor Carmen Yulín Cruz told ABC News.

Since Maria pummeled the U.S. Virgin Islands and Puerto Rico, FEMA and its federal partners have provided more than 4 million meals, 6 million liters of water, 70,000 tarps and 15,000 rolls of roof sheeting.

An additional 7 million meals and 4 million liters of water are en route to the islands by barge.

Already besieged by hurricanes ravaging the continental United States, FEMA may only now be facing the agency's most challenging recovery effort of the year.

Search and rescue efforts continue

At least 557 people and two pets in Puerto Rico and the U.S. Virgin Islands have been "saved or assisted" by FEMA search and rescue task forces, according to an agency spokesperson.

FEMA teams are continuing to operate search and rescue missions after combing through more than 2,600 structures.

With at least 5,600 personnel deployed to Puerto Rico and the Virgin Islands, Department of Defense announced it has conducted at least eight medical evacuations.

Officials say the island needs power

Gov. Ricardo Rossello told ABC News Monday that crews have been able to return power to only about 5 percent of the island's 3.4 million people. Sen. Marco Rubio, R-Florida, tweeted the same day, “Returning from #PuertoRico now. Tremendous damage. Potential for serious crisis in areas outside of #SanJuan MUST get power crews in ASAP.”

According to a FEMA press release sent to reporters Monday evening, the federal government has sent at least 281 generators to Puerto Rico and the Virgin Islands in an attempt to restore power to critical facilities until the permanent infrastructure can be repaired.

A FEMA spokesperson referred ABC News' request for information on power crews and other efforts to restore power to the island to the Department of Energy. A spokesperson at the Department of Energy did not immediately respond to ABC News.

The U.S. National Guard has deployed more than 2,500 personnel to the Caribbean to help move resources, rebuild infrastructure and provide security.

Getting resources to Puerto Rico is a challenge for recovery efforts

A FEMA spokesperson told ABC News that the agency is making progress and Trump told reporters that the challenges facing hurricane recovery efforts in Puerto Rico are different from those in Texas and Florida.

"But the difference is, this is an island sitting in the middle of an ocean. And it's a big ocean; it's a very big ocean," said the president. Trump added that he thinks FEMA is doing "a very good job."

He reiterated the government's commitment to Puerto Rico and the Virgin Islands in a press conference later Tuesday. “The recovery process will be a very, very difficult one," Tump said. "We will get through this and we will get through it together. We will be stronger. We will be bigger. We will be better.”