Shawn Lamb, 52, is charged with three counts of second-degree murder in connection with the deaths of three aboriginal women in Winnipeg. (CBC)

The investigation into alleged serial killer Shawn Lamb is in need of tips from the public.

A national tip line was launched in July and police say they have received information from dozens of callers but they need more.

And they also need to go back to some people who have already called.

Const. Jason Michalyshen won't reveal the new information that has been received but people who have already used the line anonymously are urged to call back.

Police have charged Lamb, 52, 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.

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

Police are not ruling out further charges and are talking with forces in other provinces to see if Lamb may be connected to cases elsewhere.

Police in at least two other Canadian provinces — Quebec and Alberta — have said they are probing possible links to unsolved cases in their communities.

TIP LINE

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Toll free: 1-855-817-4949

Local: 204-986-7567

With files from The Canadian Press