The U.S. Secret Service is moving forward in granting Republican presidential candidates Donald Trump and Ben Carson with 24-hour protection.

Trump, the GOP front-runner, reportedly called for Secret Service protection due to the large crowds attending his campaign rallies, while Carson's campaign said the retired neurosurgeon has received an increased number of threats.

The U.S. Department of Homeland Security announced that they received official requests Monday for protection from both campaigns, which are now being reviewed.

"The Department of Homeland Security has now received official requests for Secret Service protection from both the Carson and Trump campaigns," spokesman SY Lee said, reports Reuters.

The Secret Service then reportedly sent letters Monday to congressional leaders who have to sign off on the proposal. If and when their requests are approved, each candidate would receive a rotation of 260 Secret Service agents to provide them with 24-hour protection.

"As prescribed by statute, authorization for Secret Service protection for presidential candidates is determined by the Secretary of Homeland Security after consultation with a congressional advisory committee which includes the Speaker of the House, House Minority Leader, Senate Majority Leader, Senate Minority Leader, and one additional member selected by the aforementioned committee," the Homeland Security spokesman said, according to ABC News.

In addition to reporting about Trump and Carson's Secret Service request over the weekend, Newsmax also reported that there will be a heavy upgrade to Democrat front-runner Hillary Clinton's detail.

While speaking to ABC News on Tuesday, Carson denied that his campaign requested protection, claiming that Secret Service and FBI approached him.

"Actually Secret Service and FBI came to our campaign and they said we need Secret Service protection," Carson said. "The bottom line is there's been a lot of threats so obviously it's considered legitimate."

Trump, on the other hand, has been outspoken in calling for Secret Service protection since his rallies have become large.

"We're getting the biggest crowds," he told Fox News host Greta Van Susteren last Thursday. "If I was a Democrat, they'd have it but it's really up to them. They know what they're doing, and I assume they're doing the right thing. I would hope they are doing the right thing."