"At this stage her injuries do appear to be consistent with having been struck by a vehicle.
"We believe Charlotte was walking on the stretch of the A90 between Fordoun and Laurencekirk, which is approximately nine miles north of Stracathro services, between 4am and 5am on Saturday morning.
"I am grateful to the members of the public who have contacted us so far and we have officers following up on those calls. I would, however, like to renew our appeal for anyone who may have seen Charlotte on this section of the A90 to contact us as soon as possible."
Miss Tennant was wearing dark jeans, a white T-shirt, a light blue denim shirt and white trainers when the incident happened.
Anyone with information is asked to contact police on 0845 600 5700 or Crimestoppers in confidence on 0800 555 111.