Members of criminal organizations are intimidating customs workers at Montreal's Pierre Elliott Trudeau International airport, a study conducted for the union that represents customs officers suggests, Radio-Canada reports.

CBC's French language network reported Monday that the study shows private investigators discovered that alleged mobsters had given money to workers in exchange for their help in some cases.

The airport is one of the busiest in Canada.

The alleged mobsters intimidated the customs officers and stopped them from searching some aircraft, Radio-Canada reported.

Such security breaches could have allowed criminals to move drugs through the airport , Radio-Canada said.

Jean-Pierre Fortin, vice-president of the customs officers' union, told Radio-Canada that customs officers received instructions from people not in uniform, whom they did not know and who held no positions at the airport.

Fortin said when he found out this practice was occurring, he questioned who was responsible for providing airport security.

Earlier this month, Montreal's airport authority promised it would review security at the airport after the newspaper La Journal de Montreal reported that one of its journalists was able to enter seven restricted areas of the airport and to walk onto the tarmac.

With files from the Canadian Press