Backup copies of Hillary Clinton's emails from her tenure as secretary of state have been found in the hands of a second company that stored them in a "cloud" storage system without anyone even knowing about the arrangement until recently, reports McClatchy. The firm, Datto Inc., said the emails have been given to the FBI, which is investigating whether Clinton's use of a private server put classified information at risk.

Datto's involvement was made public on Tuesday when Sen. Ron Johnson, R-Wis., the Senate Homeland Security chairman, sent a letter to the company seeking information about its role in managing Clinton's emails.

The original company hired by Clinton to manage her private email system after she left the State Department, Colorado-based Platte River Networks, apparently hired Datto in 2013 to make a cloud-based backup of the server, and then forgot about the arrangement, which may have resulted from a misunderstanding, according to McClatchy.

Although a spokesman for Platte River said the company never asked Datto to make copies of the emails and store them on an offsite cloud server, and claims it was never billed for the server either.

It's not clear whether the FBI will be able to recover any of Clinton's emails from Datto, or even if the data provided to the company includes material from her time as secretary of state, according to The Washington Post.

Clinton turned over some 30,000 work-related emails to the State Department in December for record-keeping purposes, and deleted an additional 30,000 emails that she unilaterally deemed personal in nature.

Congressional investigators view the decision to delete her emails as a red flag, and believe Clinton may have violated numerous laws by storing and transmitting classified data on her private system.

In their ongoing investigation, the State Department and intelligence agencies have found more than 400 emails containing classified information, including at least two classified as "top secret" at the time they were sent, among the highest classifications. Clinton maintains that none of the emails were marked classified at the time they were sent, according to Politico.