A Niagara Falls man already in custody has been charged with a second count of first-degree murder, and local police say his possible involvement in three other killings is being investigated..

Michael Durant, 33, was charged with first-degree murder on Monday in the death of Diane Dimitri, a sex-trade worker who disappeared in August of 2003.

Durant was already facing a similar charge in the death of Cassey Chihocki, an exotic dancer whose body was found in a desolate wooded area on the outskirts of Niagara Falls on Jan. 24.

At a news conference on Monday, police confirmed they were investigating any ties between the accused and three other killings, dating back to 1995.

They said the cases had certain commonalities, including the fact that all the victims were in the same line of work (either prostitution or exotic dancing), all the bodies were found in the Niagara area and all but one of the victims was known to frequent the city of Niagara Falls itself.

The three other cases being probed are those of Dawn Stewart, 32, Nadine Gurczenski, 27 and Margaret Jugaru, 26.

With files from Canadian Press