Officials are calling the devastation in Puerto Rico a humanitarian disaster. Six days after Hurricane Maria hit, millions are struggling for basic necessities like adequate food, water, fuel and electricity. Eighty percent of the island's transmission lines are down, and power may not be restored for more than a month.

In a series of tweets Monday night, President Trump said the U.S. territory's old electrical grid was "devastated." He also appeared critical of the island's financial problems, tweeting they owed "billions of dollars to Wall Street and the banks which, sadly, must be dealt with."

FEMA has sent out over 10,000 federal forces to work around the clock, reports CBS News' David Begnaud. Supplies are coming in slowly from the U.S. mainland to help millions still struggling across the island.

Tap here to