A Facebook post for staff said: "The information included names, addresses and bank account details of colleagues. This affects colleagues from all levels of the organisation.
"We are taking this extremely seriously. Dalton Philips is leading the response."
But one person commented on the site: "I haven't been informed of this and shouldn't have to read it on here."
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Getting brighter this afternoon, cloudy and damp to the east
Brisk winds ahead
Final preparations are underway in Leeds for a record-breaking dance event. The Big Disco will see traffic diversions in the city.