The FBI investigation of Hillary Clinton’s email has now expanded to include obtaining data from a second tech company, which is fully cooperating with the FBI probe that has threatened Clinton’s bid for the Democratic presidential nomination, Fox News has learned.

A source familiar with the investigation told Fox that the FBI contacted Connecticut-based Datto, Inc. in September and asked them to preserve all data they had which may be connected to Clinton. Datto was hired to help back up data in May 2013 by Platte River Networks, the Colorado-based tech company that managed Clinton’s server and has already been cooperating with the FBI investigation.

The cooperation of a second tech company raises new questions about whether the FBI is now obtaining any of the emails that Clinton says she and her attorneys deemed to be personal and deleted, as Republican critics have demanded to know if any of those emails were really work-related emails that should have been turned over to the State Department along with other federal records.

Datto's cooperation also raises more questions about whether anyone at the company, where employees do not have security clearances, had access to classified information that was in Clinton’s server. The source familiar with the investigation said that like all major tech companies on the front lines, Datto has faced cyberattacks, another subject of great interest to the FBI in its probe of Clinton’s server.

The FBI investigation gathered new steam this past Friday when officials at Datto received written consent from both Platte River and Clinton’s camp to turn over relevant data to the FBI, a process that is now underway as Clinton struggles in the polls just days before the first Democratic presidential debate in Las Vegas.

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However, the source familiar with the investigation stressed it’s not clear whether Datto has in its possession all of Clinton’s personal and officials created while she was Secretary of State -- or new emails or other data created after she left office.

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The confusion comes from the fact that Datto was hired by Platte River and not the Clinton team, so the company had no idea it was backing up data for Clinton until August of this year when company officials read news reports about Platte River having the high-profile contract.

Once Datto officials realized this summer that they had been backing up some of Clinton’s data which was now the subject of an FBI probe, one company official recalled, “there was a collective lump in our throats” and they sought to cooperate fully.

Datto’s involvement was first revealed by Senate Homeland Security Chairman Ron Johnson, R-Wis., who is investigating the security of Clinton’s server, and sent a letter to the company this week seeking more information.

Aides to Johnson have privately expressed interest in emails among Platte River officials about whether there was a record of a “directive to cut the backup” of Clinton’s data.

In August, Johnson wrote, an employee at Platte River voiced suspicions over searching for an email from Clinton Executive Service Corp. directing such a reduction in data being stored in October or November 2014 and then again around February, advising Platte River to save only emails sent during the most recent 30 days.

“Starting to think this whole thing really is covering up some shaddy [sic] s---,” the Platte River employee wrote.

When employees at Platte River discovered that Clinton’s private sever was syncing with an offsite Datto server, one Platte River employee wrote in an email, “this is a problem.” 

Clinton campaign spokesman Brian Fallon fired back at Johnson's efforts on Wednesday, saying in a statement that the senator is "ripping a page from the House Benghazi Committee's playbook and mounting his own, taxpayer-funded sham of an investigation with the sole purpose of attacking Hillary Clinton politically." He said the Justice Department is "fully aware of Datto's role" in providing services to Platte. 

A Clinton aide also said the Clintons did not negotiate the arrangement with the back-up services company, and the campaign supports the company turning over any equipment to the Justice Department. 

The source familiar with the investigation stressed there was no conversation between employees of Datto and Platte River about covering up any data. Though the source noted that this summer Platte River employees were “surprised” to learn that the Clinton data was being backed up in an offsite cloud, which wasa more extensive backup than Platte River officials had anticipated. As a result, officials at Datto took steps in August to make sure the Clinton data was being preserved because they did not want to run into a legal problem.

Michael Fass, general counsel at Datto, would only comment on the company’s general decision to cooperate with the FBI probe.

“With the consent of our client and their end user, and consistent with our policies regarding data privacy, Datto is working with the FBI to provide data with its investigation,” Fass told Fox in an emailed statement that referenced Platte River as well as Clinton.

Fass added in the emailed statement late Tuesday, “Also, we received a letter from the Senate Homeland Security Committee and Government Affairs Committee just last night and we are in the process of responding to it. Datto is a data protection and business continuity company that provides backup data storage to thousands of Managed Service Providers, including Platte River Networks. Datto has no role in monitoring the content or source of data storied by MSP clients such as Platte River.”

Fox News' Jake Gibson contributed to this report.

Ed Henry currently serves as Fox News Channel's (FNC) chief White House correspondent. He joined the network in June 2011.