In January 1994 Halphen began an inquiry following the discovery of a series of forged invoices between Jean-Claude Méry [fr] and companies that were providing services to HLMs (subsidised low-cost housing) in Paris.

The inquiry also investigated the conduct of the HLM office in the neighbouring Hauts-de-Seine département, at the time run by Didier Schuller and Patrick Balkany, close associates of Charles Pasqua.

In 1996 the former vice president of OPAC – the public body controlling low-cost housing – François Ciolina, exposed corruption surrounding the HLM apartment owned by the son of Jean Tiberi, the mayor of Paris.

The following year, shortly after the death of Jean-Claude Méry, the newspaper Le Monde published the contents of a film made in December 1995 by journalist Arnaud Hamelin.

In the tape, Méry spoke of how he had delivered 5 million Francs in cash to Michel Roussin, chief of staff of then prime minister Jacques Chirac.