(By Sandra Cordon)). Rome, June 3 - Senator Aldo Di Biagio, a member of ex-premier Mario Monti's Civic Choice party, and three other people are under investigation in an alleged social security fraud involving as much as 22 million euros, sources said Monday. Di Biagio, 48, is suspected of criminal conspiracy and criminal association in a probe into an alleged fraud to siphon millions of euros from Italy's social-security agency INPS and the justice ministry. At least four people, including lawyers and civil servants, are facing arrest in connection with the alleged fraud, judicial sources said. They are suspected of criminal association, fraud against the Italian State, forgery and money laundering involving the INPS fund. INPS is the fund that Italian workers pay into for their retirement pensions. It also handles many benefits, such as disability and unemployment benefits. Paola Della Monica, the investigating judge, issued arrest warrants on Monday for four people. In judicial documents, she accuses Di Biagio - who was only elected to the Senate three months ago - of directly benefiting from the fraudulent receipt of 443,589 euros found in bank drafts issued by Banca Intesa Sanpaolo. Others named in the various documents include Nicola Staniscia and Gina Tralicci, according to investigators. It's believed the overall scam involved false claims and appeals against the INPS, to obtain increased benefits. However, many names that were used in these claims belonged to Italian residents who were dead or had moved to other countries. The proceeds of the fraudulent activities were used to buy property in Italy and or hidden in bank accounts in other parts of Europe and in Panama, according to investigators. Di Biagio is a former head of the International relations office in the ministry of agriculture and forestry and became a parliamentarian with ex-premier Silvio Berlusconi's People of Freedom (PdL) political party. However, in July 2010 he left the PdL to join a group of politicians who formed a new group, the Future and Freedom for Italy. Then, in February's national general election he was nominated to the Senate election list for Monti's Civic Choice party and won election. Investigators are now moving to seize property, documents, and exercise arrest warrants, authorities say.