The national tip line into alleged serial killer Shawn Lamb is being shut down by Winnipeg police.

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Shawn Lamb, 52, is charged with three counts of second-degree murder. (CBC)

The tip line was launched in July as part of the police service's investigation into Lamb, 52, who is charged Lamb with three counts of second-degree murder in the deaths of three aboriginal women — Tanya Nepinak, 31, Carolyn Sinclair, 25, and Lorna Blacksmith, 18 — all of whom disappeared in the last year.

Sinclair's body was found in a dumpster behind an apartment complex on Notre Dame Avenue in March 2012, while Blacksmith's body was found in a yard on Simcoe Street in June 2012.

The body of Nepinak, who went missing last September, has yet to be found but police believe she is dead.

The tip line will close later today, police stated in a news release, but did not explain why.

The homicide unit continues to co-ordinate the investigation, the release said.

Anyone with information about the investigation is asked to call the homicide unit at 204-986-6508 or Crime Stoppers at 204-786-TIPS (8477).