Police have arrested a 47-year-old man in relation to the killing of Melbourne woman Sarah Cafferkey.

Ms Cafferkey, from Bacchus Marsh, went missing earlier this month and her body was found in a house at Point Cook, in Melbourne's south-west, in the early hours of Sunday morning.

Police earlier said they wanted to speak to 47-year-old Steven Hunter over the 22-year-old's killing.

This morning police said they had arrested a Bacchus Marsh man at a house in Hawthorn around 12:30pm (AEDT).

The man is currently in custody and assisting police with their enquiries.

Hunter, 47, exchanged Facebook messages with Ms Cafferkey in the days before she disappeared, and police said they were treating him as a person of interest.

It is believed Hunter was living or staying in the house in Fongeo Drive, Point Cook, where Ms Cafferkey's body was found.

Police have warned people not to use social media to post "hateful or inciteful" comments which could prejudice any upcoming court case.

Investigators spent yesterday combing the Point Cook house for forensic clues.

They retrieved several bags of evidence and dusted a car outside the house for fingerprints.

Detectives also revisited neighbouring homes to interview residents.

Police had already ruled out an ex-boyfriend of Ms Cafferkey's as a person of interest.