HALDIMAN COUNTY, Ont. - Police have charged a former Catholic priest with a historical sexual assault investigation in southern Ontario.

Ontario Provincial police say they have been investigating an alleged sexual assault in 1975 involving a boy who was 13 years old at the time.

They say the alleged incident occurred while the accused was a priest at St. Stephen's Roman Catholic Church in Cayuga, St. Kevin's Roman Catholic Church in Welland and St. Thomas More Roman Catholic Church in Niagara Falls.

Donald Grecco, 75, of Peel Region is charged with one count of gross indecency and one count of indecent assault on a male.

Grecco was also charged three weeks ago with two charges of gross indecency and two charges of indecent assault on a male in alleged incidents that occurred between 1977 and 1982 involving two boys who were 10 and 14 years old at the time.

In 2010, Grecco pleaded guilty to sexually molesting three altar boys in the 1970s and 80s.