A man and a woman continue to be questioned on suspicion of the murder of a 60-year-old man after a 19-year-old is released on police bail.
The man, who was found in Broad Street in the Pill area of Newport, at 4am yesterday, was pronounced dead at the scene.
He was subjected to a serious assault and may have been hit by a vehicle while lying in the road, police said.
Gwent Police yesterday arrested three people on suspicion of murder but confirmed a 19-year-old man has been released on bail.
Two other people, a 25-year-old man and a woman, 23, both from Newport, remain in custody on suspicion of murder.
Police also continue to hold a further four people, two men, aged 22 and 44, and two women, aged 18 and 46, over suspected driving offences.
The four, from the Newport area, have been arrested on suspicion of causing death by careless and inconsiderate driving and failure to report a road traffic collision.
Broad Street, which was cordoned off yesterday, remains closed while investigations continue, police said.
Officers are appealing for anyone who was in the area of Broad Street between the hours of 2am and 4am yesterday to contact them.
Anyone who has any information can contact Gwent Police on 101 or call Crimestoppers anonymously on 0800 555111.