DYFED Powys Police is investigating a report of assault and false imprisonment.
The incident took place sometime between 4pm until 6.15am on Sunday, January 1, at a property on Cwrt Pandora, North Dock and Marine Street in Llanelli.
A local 24-year-old man has been arrested in connection with the incident.
Officers are now appealing for witnesses who may have heard or seen something in the area at that time, or anyone with information to come forward to help them piece together exactly what happened.
To provide information call police in Llanelli on 101 quoting crime reference ALT/0953/01/01/2017/01/C.
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