Megan, aged 20, was reported missing after not returning from a night out with her friends in York city centre on Wednesday 22 January 2014.
Megan had been to Popworld on George Hudson Street where she stayed until the early hours of Thursday 23 January 2014.
Officers have been reviewing CCTV footage to try and trace Megan’s movements after she left the bar and have established that she was with a group of people on the corner of Rougier Street near Lendal Bridge at around 2.20am.
The group were seen a short time later at the other side of Lendal Bridge, on Museum Street but Megan was not with them.
Officers need to find out where Megan went after she was last seen on CCTV and are appealing to anyone who saw a woman matching her description in the early hours of Thursday morning to get in touch.
Megan is described as white, around 5ft 6in tall, of medium build with long dark brown hair. When she was last seen she was wearing a cream knee length dress which had large brown and orange flowers on it and black plimsoll type shoes.
Superintendent Phil Cain, of North Yorkshire Police, said: We are a very concerned for Megan’s welfare and are urging the public to help us establish her movements in the early hours of Thursday 23 January 2014.
As with all missing persons enquiries we are doing everything we can to locate Megan and make sure she is safe and well.
Her disappearance and the fact that she has not had any contact with her family and friends for almost five days now is extremely unlike her and adds to our concern.
Megan’s family are understandably very distressed by her disappearance and I would appeal for anyone who has any information at all about where she might be to get in touch with the police as soon as possible.
Specially trained officers are offering support to Megan’s family at this extremely difficult time.
Officers from the regional underwater search unit and specialist search officers from North Yorkshire Police are conducting riverbank searches along the River Ouse in York city centre today.
Anyone with information which can help officers to find Megan is urged to contact North Yorkshire Police on 101 – select option 1 – and pass information to the Force Control Room.
The appeal to trace Megan Roberts is also being supported by the Missing People charity. Information from the public – or from Megan herself – can be passed on free of charge and in confidence by calling 116 000.