PORT-AU-PRINCE, Haiti (AP) — Scientists are presenting the strongest evidence yet that U.N. peacekeepers imported the cholera strain that has killed more than 5,500 people in Haiti.

The study is published in the July issue of the Emerging Infectious Diseases journal of the U.S. Centers for Disease Control and Prevention.

Its findings "strongly suggest" the U.N. contingent from Nepal contaminated a Haitian river because of poor sanitation at a base.

Lead author Renaud Piarroux previously blamed peacekeepers. This study is more complete and its methodology was reviewed by other scientists.

It also argues for the importance of accurate field investigations. The U.N., CDC and World Health Organization initially refused to investigate the outbreak's origin.

Related Final report of the independent panel of experts on the cholera outbreak in Haiti