By Deena Zaru, CNN

(CNN) -- Rihanna criticized President Donald's Trump response to the humanitarian crisis in Puerto Rico following Hurricane Maria, suggesting that the President is not paying enough attention to the disaster occurring on the island.

"Dear @realDonaldTrump I know you've probably already seen this, but I just wanted to make sure! Don't let your people die like this," the pop star tweeted early Thursday morning, along with a cover of the New York Daily News that reads, "Puerto Rico needs more help, Mr. President!"

CNN has reached out to the White House but a request for comment was not immediately returned.

In a second tweet, Rihanna called for a "round of applause" for former US Presidents Bill Clinton, George W. Bush and Barack Obama, who made an appearance at the Presidents Cup golf tournament in New Jersey on Thursday, following a joint effort by the five living former presidents to support hurricane relief efforts.

"Round of APPLAUSE to these gentlemen for taking control of this devastating situation!!! #CaribbeanGirl #OneLove," she wrote.

As the crisis continues with many residents still seeking access to food, electricity, medicine and water, many celebrities, including Lin-Manuel Miranda, Jennifer Lopez and Pitbull, have also urged swift action to aid Puerto Rico. Some have also slammed Trump for what they say is a slow response.

"FYI, @realDonaldTrump, Puerto Rico is part of U.S. Territory and should be given the help they need by our government," actress Alyssa Milano tweeted.

The White House authorized a waiver on Thursday to loosen shipping rules regarding Puerto Rico that island officials say would be a significant help for recovery efforts.

Acting Homeland Security Secretary Elaine Duke, who is leading the Hurricane Maria response, defended the administration's handling of the crisis Thursday saying she is "very satisfied" with the federal government's recovery role.

"I know it's a hard storm to recover from but the amount of progress that's been made, and I really would appreciate any support that we get. I know it is really a good news story in terms of our ability to reach people and the limited number of deaths that have taken place in such a devastating hurricane," Duke said.

Florida Sen. Marco Rubio told CNN on Thursday that the federal government is responding to Maria with the same urgency as Harvey and Irma, but there are bigger logistical challenges in Puerto Rico.

These comments come after Trump intensified his personal involvement in the crisis earlier this week amid criticism that his response to the devastation there has been lackluster.

As the storm ravaged Puerto Rico over the weekend, Trump sparked and then escalated a feud with the NFL over players who refuse to stand for the National Anthem.

"Mr. President shut the f--- up about NFL. Do something about our people in need in #PuertoRico. We are American citizens too," Marc Anthony, who announced a relief initiative with Jennifer Lopez, tweeted on Monday.

"I wasn't preoccupied with the NFL," Trump told reporters on Tuesday.

The President also defended his handling of the crisis in Puerto Rico, saying, "The governor said we are doing a great job."

Puerto Rico's Gov. Ricardo Rosselló said that the island now faces a humanitarian crisis after Hurricane Maria brought violent winds and flooding. The storm also damaged a dam that put downstream residents at risk of catastrophe.

Trump is expected to visit the island on Tuesday.