I've done that, and their reply was "Due to workload factors not related to your case, USCIS anticipates a delay in completing your case. USCIS is committed to adjudicating immigration benefits in the order received and in a timely and efficient manner."
I also contacted the congressman and they replied to her the following " As a part of a greater eligibility determination, U.S. Citizenship and Immigration Services (USCIS) conducts background and security checks on applicants and certain petitioners for immigration benefits. These checks are necessary to ensure United States national security and public safety interests. In some cases, the results of these checks require USCIS to perform additional inquiries or consult with other government agencies. When this is necessary, there is often some delay in resolving the checks, and it is difficult to predict when resolution will be completed. Please be assured that this case has not been overlooked. Once all checks are resolved, the application will be interviewed, adjudicated and your constituent will be notified of the decision."