Police said on Monday that the investigation is “fast-moving” and urged people not to speculate.
The force tweeted: “We would like to thank you all for your concern and for sharing our appeal to help locate Marnie.
“Marnie is still missing at the current time, and we would ask you to contact us if you have any information that can assist the investigation.
A force spokesman added: “At this stage, we are unable to comment on specific lines of inquiry, other than to say we have a number of active lines of inquiry which are being investigated as a priority.”
Posting on Facebook, Atik said: “We are really concerned about the disappearance of Marnie Clayton and we have been working with the police all weekend on their investigation, and will continue to do so.
“We join everyone in hoping she is found safe and well.
“If anyone has any information, please contact the police on 101, quoting reference
43220021633 and if you see her or think you’ve seen her, please contact 999.”
Teenage girl missing after leaving Windsor nightclub in early hours of Sunday
eta:
Staff at a Windsor nightclub where an 18-year-old girl was last seen before she went missing say they are "really concerned" for her welfare.
A spokesman for the Atik nightclub confirmed that CCTV footage has been handed over to the police to assist in the investigation into Marnie Clayton's disappearance.
The teen, from Bracknell in Berkshire, was reported missing after she left Atik, in William Street at around 2am on Sunday morning, Thames Valley Police said.
She did not return home and was reported missing by her family just before 3am.
The Windsor nightclub said staff had been assisting officers with the investigation all weekend as the investigation into Ms Clayton's disappearance stretches into a second day.
Nightclub shares CCTV with police in search for missing teen Marnie Clayton | ITV News