A woman was seriously hurt in an attack, say Cumbria police.
Officers have appealed for a potential witness to the incident and a taxi driver to contact them urgently.
The victim, a 30-year-old, sustained serious injuries during the assault, which police are classing as GBH.
Two women, aged 36 and 25, from Whitehaven, who were arrested have been released while inquiries continue.
Police are keen to trace the possible witness and the taxi driver who picked up a lone female passenger between midnight and 2am on July 2 from Whitehaven town centre and took her to Derwentwater Road.
Anyone with information should call 101 and quote reference 020717/46 or contact Crimestoppers on 0800 555 111.
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