Police have been granted a further 36 hours to detain and question the suspect.
Detectives are calling for witnesses following a series of hit-and-run incidents in Cardiff on Friday.
A 31-year-old man has been arrested on suspicion of murder.
Hundreds gathered to share their grief at a sombre church and prayer service after a hit-and-run rampage left one mother dead.
The shocked community of Ely in Cardiff will gather to pray for the victims of Friday's terrible hit-and-run attacks in the Welsh capital.