Hundreds of local authority workers have had their personal details posted online following a data leak.
City of London Police is looking at whether to launch an inquiry after around 750 staff at Medway Council in Kent had their details published on a website.
The data included their names, gender, dates of birth, staff identity numbers, contract start dates and working hours but there has been no disclosure of bank details.
The local authority said it has immediately terminated its contract with the firm which held the data, Diagnostic Health Solutions (DHS) Ltd, over what it described as an "unacceptable data breach".
But the company said it was the victim of theft and maintained its systems were 100% secure.
A DHS spokesman said the website on which the data appeared was shut down within two hours of them discovering it.
Four other clients of DHS, including private sector firms and other local authorities, were also affected by the leak, representing about 5% of its customer base.
A Medway Council statement said: "The council has terminated its contract with the contractor Diagnostic Health Solutions Ltd following a breach of personal data that the firm holds on employees.
"The firm notified the council after details were posted on a website by a third party and police are now investigating. The website was immediately taken down.
"The details showed staff names, gender, date of birth, staff ID numbers, contract start dates and working hours, but we have assured employees that it did not include any data on people's bank details or other sensitive information.
"The council has written to the firm - which holds data on staff from numerous large private companies and public sector organisations - to terminate the contract with immediate effect following this unacceptable data breach.
"We have also informed all staff affected as well as unions and the Information Commissioner's Office."
A spokesman for DHS said: "What we believe has happened is that our software was the victim of theft at a source level."
A police spokeswoman said: "The City of London Police has received a report of theft of data from Diagnostic Health Solutions and is considering whether to launch an investigation."