Senator Chuck Grassley of Iowa, the former Chairman of the Senate Judiciary Committee, said Tuesday that he expects special counsel Robert Mueller's final report to be released "within a month."

Mueller and his team of prosecutors have been investigating Russian interference in the 2016 election and whether the Trump campaign collaborated with Moscow to tilt the race in Trump's favor since May of 2017.

A spokesman for Grassley told INSIDER that his estimates weren't based on any "specific information," but media speculation over when the probe would wrap up.

Senator Chuck Grassley of Iowa, the former Chairman of the Senate Judiciary Committee, said in a Tuesday interview that he expects special counsel Robert Mueller's final report to be released "within a month."

Speaking to radio host Hugh Hewitt, Grassley also said he hopes for as much transparency as possible whenever Mueller's report is made public.

"I don’t care what the report says," Grassley said. "The public oughta know what their 25 or 35 million bought. And except for national security and privacy of individuals... everything else I think oughta be out."

While the Department of Justice guidelines governing special counsel operations only require Mueller to submit a final report to the attorney general, President Donald Trump's attorney general nominee William Barr indicated in his confirmation hearings that he would make as much of the report available to the public as possible.

Mueller and his team of prosecutors have been investigating Russian interference in the 2016 election and whether the Trump campaign collaborated with Moscow to tilt the race in Trump's favor since May of 2017.

Mueller has indicted three Russian companies and 35 individuals in the probe, including eight Americans affiliated with the Trump campaign or administration.

Read more: Here's everyone who has been charged and convicted in Mueller's Russia probe so far

In an email to INSIDER, Grassley spokesman Taylor Foy said the senator's estimates "weren’t based on any specific information, but rather growing media speculation and reports that it may be wrapping up."

For months, media outlets have speculated when the notoriously secretive Mueller probe would end. As Foy noted, NBC News reported in December that Mueller could submit his final report as soon as the middle of this month.

In a January 28 press conference, acting Attorney General Matthew Whitaker became the first senior Justice Department official to offer a clue as to when the investigation would conclude.

"Right now the investigation is, I think, close to being completed," Whitaker told reporters. "And, I hope that we can get the report from director Mueller as soon as possible."

Read more: Trump said 'you have to get rid of' the Russia probe and parroted a Kremlin talking point in a wide-ranging interview

Some DOJ veterans said Whitaker's seemingly off-the-cuff remark was inappropriate, since Mueller probe still has several loose ends to tie up. They also cautioned against taking Whitaker's comment at face value, given recent media reports suggesting there are still several other shoes expected to drop in the Russia probe.

Former Trump campaign officials Rick Gates and Michael Flynn are still cooperating with Mueller until at least March. Mueller is also engaged in a legal battle with Paul Manafort over alleged breaches of his plea agreement, and a federal judge recently extended the DC grand jury reviewing evidence in the Mueller probe until the summer.