UK software company Sage's data has been breached, compromising personal information for employees at 280 UK businesses.
The investigating agencies are probing the "unauthorised access" to data which is most probably done by someone using an "internal" company computer login.
The information was accessed many times over the past few weeks.
It is not clear whether hackers were able to steal data from the FTSE-listed firm, or merely viewed.
The company says, "It is taking the breach extremely seriously", they provide business software for accounting and payroll services to firms across 23 countries.
A Sage spokesperson said: "We are investigating unauthorised access to customer information using an internal login.
"We cannot comment further whilst we work with the authorities to investigate - but our customers remain our first priority and we are speaking directly with those affected."
The Information Commissioner's Office (ICO), responsible for the enforcement of the Data Protection Act 1998, has also been informed.
Sage has notified it's all businesses partners who might have been affected by this hack and has advised them to look out for any unusual activity.
Sage was founded in 1981 and now has more than 13,000 employees around the world.