Police want to hear from anyone who was in the area at the time, especially a person known to have been walking a small black dog at that time and who may have seen what happened to the girl or noticed the attacker running away.
Previously, Wairarapa CIB had warned anyone walking alone - particularly at night - to take precautions to keep themselves safe.
In the earlier incidents, a 14-year-old girl was allegedly sexually assaulted in Colombo Rd in September, about 9.30pm on a Saturday.
A man, 23, is facing charges in Masterton District Court.
In August, a 14-year-old girl was forced down a bank near the swing bridge and police believed it was a sexually motivated attack. The incident happened about 5pm on a Saturday. A boy, 16, has been referred to Youth Aid.