Two assaults involving four people known to each other reportedly took place on the same night in Scunthorpe.
The first involved two men and happened on Scotter Road at around 10pm on Friday.
Officers want to speak to a man walking his dog in the area at the time who may have seen it.
The second alleged assault happened a shortly after on Shakespeare Avenue. It was reported that two men and a woman assaulted a man.
Officers think another lady witnessed the incident and spoke to those involved.
Two men and a woman have been arrested in connection with the incidents. All three have been released under investigation.
Anyone with information is asked to call 101, quoting investigation 16/35383/18.