Updated May 30, 2015 15:05:42

A man and a woman have been tied up in an early morning armed robbery in central Victoria that police say may have been a case of mistaken identity.

Police said two men, who were armed with a gun and wearing yellow fluorescent vests with the word "police" on them, entered the Lancefield property through an unlocked door about 2:00am on Friday.

The pair woke a 42-year-old man and 36-year-old woman and tied them up while they searched the home for money.

Police said the woman was then taken into a bedroom where she was threatened and sexually assaulted.

The two men then left in a car.

Detective Sergeant Shane Manuell said police were investigating a number of theories as to why the house was targeted.

"The offenders were making demands for money, which the victims didn't have," he said.

"We believe at this early stage that this may have been a case of mistaken identity or an instance where the offenders have been given the wrong information about this address.

"This would have been a terrifying experience for these people and we are appealing for information from the public to help us catch these offenders."

The men were described as wearing dark-coloured balaclavas that covered the bottom half of their faces.

Police have asked anyone with information to contact Crime Stoppers.

Topics: police, sexual-offences, armed-robbery, lancefield-3435, vic

First posted May 30, 2015 13:02:57