RIO DE JANEIRO — Boxer Arturo Gatti’s death was ruled a suicide by police Thursday and a a judge ordered the release of his wife, who was once suspected of killing the former champion.

Lead investigator Paulo Alberes told The Associated Press that authorities decided Gatti killed himself on July 11 while at a seaside resort in northeastern Brazil.

When asked if police had determined the case was a suicide, Alberes said ‘‘yes.’’ He offered no other details.

A day after the 37-year-old Gatti was found dead, police said that his Brazilian wife, Amanda Rodrigues, had strangled him with her purse strap as he drunkenly slept.