A 20-year-old man has been arrested on suspicion of murder in connection with the disappearance of a student in his first week at university.
Thomas Jones, 18, was last seen near the River Severn in Worcester during the early hours of Wednesday.
West Mercia Police had earlier identified two men they wanted to speak to after releasing CCTV images recorded at nearby Velvet nightclub.
The arrested man is currently in police custody.
Hundreds of volunteers have joined police with the search and officers have been “working around the clock” to find Mr Jones, the force said.
Det Insp Mark Bellamy said: “A number of lines of inquiry are currently ongoing and I hope today’s developments will assist us in our continued investigation.
“Thomas’s family has been made aware of the update and they are being supported by specially trained officers.”
Police believe Mr Jones crossed the Sabrina footbridge, near Worcester Racecourse, and then walked on to the footpath that runs along the top of the flood defences on Hylton Road in the direction of Hallow, just before 0350 BST.
The force said the hundreds of volunteers supporting the investigation was an “unprecedented response”.
Searches are ongoing, but police have asked people to “kindly stay away” from the area so officers and divers can work “without distraction”.
People have been asked to check CCTV video, dashcams and garden sheds.
Mr Jones’ aunt, Jackie Rogers, said a “small army” was carrying out house-to-house inquires in and around Hylton Road and were determined to “find our boy”.
Mrs Rogers said the teenager sent a Facebook message to a friend at 03.46, but no-one had heard from him since.
The student, from Bromsgrove, was starting a primary teaching course at the University of Worcester. He had only moved on 16 September.
Divers from South Wales Search and Rescue have searched the river near Worcester Rowing Club on Grandstand Road.
The teenager was believed to have been wearing pale-coloured jeans, a navy blue, woollen zip-up Lacoste top and green shoes at the time of his disappearance.
Appeals were also made by West Brom Football Club, as he is a season ticket holder at The Hawthorns.
The Baggies shared his details on the big screen at the match against Millwall. Rivals Aston Villa also publicised the search.