The Agency Field Operations Section responds to all complaints received from consumers. Response to complaints concerning health related problems occurs as soon as possible and in no case later than 24 hours; most other complaint responses occur within 72 hours. Response to consumer complaints requires investigation into the cause of the complaint and possible resolution of the problem. FOS knows that health-related complaints, if neglected, may become emergencies. Initial contact with the complainant is by phone; a letter is written or personal visit made if telephone response is unsuccessful. After the complaint has been investigated and the problem resolved, a follow-up letter may be sent to the complaintant.