The developer of the Bleachbit software told the Daily Caller that the FBI may not have been able to detect its use in scrubbing the private email server used by Hillary Clinton.

Andrew Ziem, the lead developer of BleachBit, says that if Clinton — or her computer technicians — used the open-source software in portable mode, such as through a USB drive, FBI investigators would not have been able to determine that someone used the product to clean Clinton’s system of its emails.

If BleachBit was downloaded, its use would be much easier to detect. Some users operate the software portably in order to “to avoid showing that a cleaning tool was used, which could look bad.”

Clinton’s use of the product, which is available for free online, was first revealed on Thursday by South Carolina Rep. Trey Gowdy.

“She and her lawyers had those emails deleted,” Gowdy said during an interview on Fox News.

He was referring to the FBI’s notes from its Clinton email investigation, which were given to Congress earlier this month on condition that they not be released to the public.

“And they didn’t just push the delete button; they had them deleted where even God can’t read them. They were using something called BleachBit. You don’t use BleachBit for yoga emails or bridesmaids emails. When you’re using BleachBit, it is something you really do not want the world to see,” Gowdy continued.

In Dec. 2014, Clinton gave the State Department 30,000-plus work-related emails. She withheld an equal number, claiming that they were personal in nature and regarded yoga routines and her daughter’s wedding plans.

But FBI director James Comey said last month that investigators recovered “several thousand” work emails that Clinton did not give the State Department.

Many details about Clinton’s use of BleachBit are unclear as Gowdy did not go into detail about what the FBI’s notes said about the product.

It is not known whether the FBI learned of Clinton’s use of BleachBit through their own forensic investigation or from a witness. It’s also unclear when the tool was used. Gowdy suggested that it was towards the time period when Clinton was deciding which emails to give the State Department. He questioned why, if Clinton wanted to delete her emails, she did not do so right after she left the agency in Feb. 2013.

It seems probable that many of the 14,900 emails recovered by the FBI were from sources other than the server. Many emails would have had multiple recipients and unless they, too, used a tool like Bleachbit, the feds would have gotten access to them.

The first batch of those recovered emails is set for release on September 13.