The attack on the 31-year-old woman occurred about 11pm on Sunday, after she had earlier become involved in an altercation with two men outside her home on Argyle St, Mornington, Detective Senior Sergeant Kallum Croudis said.
The woman had been outside her home about 10.40pm when the altercation with the pair developed and she was assaulted, receiving facial injuries, he said.
She returned to her home, but 15 minutes later opened her front door thinking her boyfriend had arrived home, Det Snr Sgt Croudis said.
Instead, she found one of the two males from the first altercation at her door.
The man pushed open the door and attacked the woman, he said.
The woman alerted police about 12.40am yesterday and was taken to Dunedin Hospital by ambulance.
She had since been released and had been interviewed by police.
She said she did not know either of the men, Det Snr Sgt Croudis said.
The man alleged to be responsible for both the sexual assault and the earlier assault in the street was described as a Maori, aged about 28, with short curly black hair, of stocky build and about 173cmtall, wearing blue jeans and a red hooded sweatshirt, Det Snr Sgt Croudis said.
The second man was Caucasian, with "shaggy" blond hair, of similar age and slightly taller, he said.
The woman's two children - boys aged 4 and 6 - slept through the attack and were not harmed, he said.
It also appeared nothing had been taken from the home.
Police called in extra CIB staff yesterday to assist with the investigation, and Environmental Science and Research staff assisted with a detailed scene examination.
A police cordon and guard was in place yesterday morning, with tape blocking access to four homes and part of the footpath.
