According to a government review, Hillary Clinton sent at least four emails containing classified information through her controversial private email account while she was secretary of state, The Wall Street Journal reports.

A letter sent to Congress yesterday from the inspector general of the Intelligence Community said information in four emails was designated as "secret." The inspector general's review found the classified information through an inspection of 40 emails, meaning many more could still exist in the thousands of other emails Clinton sent, according to the Journal.

The Clinton camp has claimed that no information sent through Clinton's personal email was classified at the time it was sent, although some information may have been retroactively classified. The review, however, determined that the information was, and continues to be, classified. Thousands of Clinton's emails are still being reviewed for public release — and in one instance, classified information has already been revealed to the public through the public release, according to the letter.

Update, 2:58PM: This story has been updated to include a report from Reuters that discredits an earlier report from The New York Times.