Missing University of Hull student Libby Squire is pictured in Paris in May 2017 during a gap year when she visited with friends Detectives today urged four possible witnesses who may have 'crucial information' about the disappearance of student Libby Squire to come forward. The 21-year-old student went missing in the early hours of February 1 after a night out - and a huge search operation in Hull has failed to find any trace of her. Now, Humberside Police believe the four men - who were in the area of the city where she was last seen - 'may have seen or heard something that could be vital'. CCTV footage shows four people on Oak Road near the junction with Clough Road, close to where Miss Squire was last seen, between 1.13am and 2.34am on the morning she vanished. The Oak Road playing fields have become a focal point in the search for Miss Squire over the past three weeks. This afternoon, Detective Superintendent Martin Smalley said: 'These four people are potentially witnesses who we need to identify and speak to as part of the investigation. 'While the footage isn't clear enough for anyone to recognise who they may be, the four people in the clips will know if they were in that area at the times given.' He urged the four people to identify themselves to police, saying they seem to have been travelling in the direction of land that has been widely searched by officers. One of the people featured in Humberside Police's CCTV footage of four witnesses, who they believe 'may have seen or heard something that could be vital' Police search Oak Road playing fields in Hull last Tuedsay as part of their investigation The first clip shows an individual, believed to be in a light coloured T-shirt and dark trousers, at first running into view on Oak Road and then walking away at 1.13am. The second clip shows a figure on a bike cycling along Oak Road towards Clough Road at 1.24am, and is then seen cycling back up Oak Road at 1.34am. The third clip shows two people, one who appears to be dressed all in dark clothing and the second in light coloured trousers and a dark top, on Oak Road at 2.34am. Oak Road playing fields have been a regular site for searches for Miss Squire, and police returned to the site today with a regional marine unit to examine the drains. According to passers-by in the area, officers were 'pumping drains out' with search teams also seen clearing out the drains which are surrounded by discarded litter. Search teams have trawled through the park with wooden sticks to scour the landscape with divers are also seen doing thorough scopes of the fishing lake. A map shows the student's movements on the night of January 31 in Hull before she vanished Police arrive to search Oak Road playing fields in Hull last Tuesday over the disappearance The Oak Road playing fields have become a focal point in the search for student Miss Squire Her parents Lisa and Russ Squire (pictured on February 4) are desperate for her safe return Mr Smalley added: 'Libby remains our priority and we are determined to do all we can to find her. Timeline: The hunt for missing Libby Squire 11pm, January 31: Libby is refused entry at Welly Club around two miles from her home and put into a taxi 11.30pm: Libby was dropped off on Wellesley Avenue - but does not go inside her house 11.45pm: Libby was seen sitting on a bench around the corner on Beverley Road. A witness says she was seen speaking to the driver of a car. 12.09am: Detectives believe Libby stayed in the area for about half an hour - but is then gone. 12.30am, February 1: A near-neighbour says she woke up after hearing 'blood-curdling' screams. February 6: Pawel Relowicz is arrested on suspicion of Libby's abduction February 8: Police ask for more time to interview abduction suspect. February 10: Relowicz is charged with voyeurism, burglary and indecency - but no charges related to Libby's disappearance. February 11: He pleads not guilty. 'There are still searches taking place as part of the investigation in and around Oak Road and also around the River Hull, with further work continuing in connection to CCTV and witnesses, as well as field experts working with us to ascertain exactly what happened that night and where Libby may be. 'Libby's family have been incredibly supportive of the investigation and my heartfelt thanks goes out to them as we relentlessly pursue every line of enquiry available, to give them the answers they desperately need.' Miss Squire was wearing a Top Shop black denim skirt and faux leather jacket and distinctive trainers at the time of her disappearance. Her mother Lisa Squire and friends helped police identify the clothes which in turn helped police to try and spot the student on hundreds of hours of CCTV they have analysed. So far police have searched properties, gardens, playing fields, gardens, waterways and a pond near Miss Squire's home and the operation continues. Suspect Pawel Relowicz, 24, remains under investigation after being questioned for four days over her alleged abduction. Miss Squire was in the area around Haworth Street, about 300 yards from her student home in Hull, until around 12.09am on Friday February 1. Earlier she was refused entry to a nightclub in the city as she was too drunk. A taxi dropped her off near her house but she walked up the road to sit on a bench instead of going inside. Humberside Police said if you believe you are in the clips or have information as to who they may be, please call 101 quoting log 163 of February 6 2019Sorry we are not currently accepting comments on this article.All rights reserved for this news site dailymail and under his responsibility