Emergency services attended the scene after a rider of an electric bike collided with a bus in Chepstow, leaving them fighting for their life.
The crash occurred on the A48 road in Pwllmeyric at approximately 5.55am on Tuesday, July 7.
The bicycle rider was transported to a medical facility where their condition is described as critical.
Gwent Police have launched an appeal for witnesses as part of their inquiries.
Officers are particularly eager to hear from anyone who may have observed the cyclist in the moments leading up to the incident.
They are calling on drivers, pedestrians, other cyclists, or anyone with relevant dashcam, CCTV or mobile phone recordings to make contact.
Those with information that could assist the investigation have been asked to reach out to Gwent Police, quoting reference 2600215220.
Members of the public can submit details by telephoning 101, accessing the Gwent Police website, or contacting the constabulary through social media platforms.