Recently, Bleach Was Used At My Office To Remove Mould

Recently, bleach was used at my office to remove mould etc. Once placed down, the office door leading to my office from the treated office, was left open and a fan used to blow the fumes. Over a period of 2 weeks, now, all four members of my office have been off sick. Individually, they were treated by separate Doctors, who stated the cause of their illness was possible food poisoning, sugar levels raised and a possible allergy. The forth member did not see a Doctor but suffered flu like symptoms, remained in bed and slept for 16 hours. After which he came good.

All suffered the same symptoms, nausea, flu like symptoms and tightness of the chest. All have since returned to work after short periods off.

I need to know if the bleach may have caused this or is it simply a very large coincidence?