Vedior NV responded to concerns from the Dutch Investors' Association (VEB) in a letter posted on its Web site Friday.

Reuters had reported that the group, VEB, said it might sue the staffing firm for shareholder losses because it didn't respond adequately to rumors of a takeover offer. Vedior shares rose more than 20% on Nov. 30 amid the rumors, according to the news agency.

Vedior, in its response to VEB, said the Dutch regulatory authority, AFM, already launched an investigation into the matter. However, it said it would meet with VEB representatives on an exploratory basis.

"At this moment it is not clear what happened exactly during those first hours after the trade commenced on 30 November and hence Vedior expects this to be fully investigated," according to a letter from Vedior Secretary J.L. Miedema. "Vedior therefore completely agrees with the necessity of the investigation currently conducted by the AFM and obviously Vedior will completely cooperate."

Randstad Holding NV on Dec. 3 announced that it made a bid to acquire Vedior. The combined staffing company would be the second-largest staffing firm in the world.