Education Secretary Betsy DeVos used her personal email accounts for government business in "limited' cases and did not always properly save messages, according to an internal investigation released Monday.

The report said DeVos sent or received fewer than 100 messages on four personal email addresses during her first 15 months in office, joining other Trump administration officials in improper email practices.

DeVos sent six emails on private accounts, including five about official business. according to the report. Investigators could not prove she followed federal law on saving official emails created on personal accounts.

“We did not identify any instances where the secretary forwarded emails from her personal accounts to her department email accounts,” the report said. It added that “the secretary’s emails related to government business were not always being properly preserved.”

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Department rules forbid employees from using personal emails for work except when their government accounts are unavailable. In those cases, employees must forward the messages to their work accounts within 20 days.

In all, the Education Department's Office of Inspector General concluded there was no evidence of “active or extensive” use of DeVos’ personal email. Her office told investigators it was taking “additional steps to identify and preserve” emails in her personal accounts.

Most of the fewer than 100 emails linked to DeVos' personal accounts were from the first six months of 2017, soon after DeVos took office, the inquiry found. Most were also from a single unidentified person recommending candidates for agency jobs.

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The report noted other emails were from people who congratulated DeVos or offered other job advice.

House Democrats requested the review in October 2017, but the inspector general’s office said it began work “well into 2018” because of staffing challenges.

Other Trump administration officials who have faced questions about private emails include Ivanka Trump, Jared Kushner, former chief of staff Reince Priebus and former senior adviser Steve Bannon.

Contributing: The Associated Press