Police are appealing for witnesses to come forward after a man was believed to have been stabbed in a Nelson street.
Officers were called out to an address in Manor Street at around 7-40pm on Thursday night where they found a man with injuries consistent with stab wounds.
Police say the 36-year-old was initially uncooperative but was then taken to the Royal Blackburn Hospital before being released later.
He has now been arrested on suspicion of assault causing actual bodily harm and is in police custody.
As part of the police enquiries, a second man was identified in Royal Blackburn Hospital as having a head injury and possibly the victim of assault - with links to the Manor Street area.
Police were hoping to speak to him today while making house to house calls.
Anybody with any information should call police on 101.