PETERBOROUGH, Ont. - A company that oversees school bus transportation for three central Ontario school boards says it accidentally posted information about students online.

Student Transportation Services of Central Ontario says an internal staff training document was "inadvertently" shared on Facebook and Twitter, while posting an update regarding bus operator contract negotiations last week.

The company, which runs school buses for the Kawartha Pine Ridge, MonAvenir Catholic and Peterborough Victoria school boards, says the document included a link that allowed access to information about students, including their date of birth and address.

It says that it removed the PDF and closed off access to the database as soon as it learned of the issue.

But it says information about a small number of students was accessed, and those affected have been notified.

The company says it has "put measures in place" to prevent this from happening again, but did not provide details.