The move followed an investigation by Swedish public broadcaster SVT's programme Uppdrag Granskning earlier this year, which revealed that the deal between the state-run maritime administration and AgustaWestland, an Anglo-Italian manufacturing company, had been set up using private Hotmail accounts.
In late April, reporters claimed that the Swedish Maritime Association (Sjöfartsverket) had scored the one billion kronor ($120 million) deal with the firm, which is owned by Finmeccanica, weeks before announcing a public tender for the project.
One of the messages discovered by the programme includes a comment by the vice director of the organisation stating that she is prepared to travel to Italy to “make a handshake” on the deal.
Late on Wednesday it emerged that police from Sweden's National Anti-corruption Unit (Riksenheten) had raided the association's offices in Norrköping, south of Stockholm, although prosecutors refused to give further details about the investigation.
“Since there is reason to believe that a crime that falls under public prosecution has been committed, I have today decided to initiate an investigation,” prosecutor Roger Engstedt told Uppdrag Granskning the following day.
The Swedish Maritime Association confirmed on its website that a raid had taken place.
“We welcome the initiative and are now cooperating with the prosecutor,” it read.
By Thursday evening AgustaWestland had not commented on the investigation.