Police are investigating the death of a 53-year-old Victorian woman who fell ill after consuming a drink at a retreat near Ballarat.

Police believe the woman was at a retreat in the regional town of Clunes, north of Ballarat, when she fell ill "after ingesting a drink" about midday on Saturday.

The Ringwood North woman died at the Fraser Street premises and two other people were taken to hospital for observation, police said.

Detectives are investigating the circumstances and have urged anyone with information to contact Crime Stoppers.