Police searching for a missing 21-year-old woman are continuing to question a man arrested in Lurgan, County Armagh.
Chloe Mitchell was last seen in central Ballymena late last Friday night, into the early hours of Saturday.
The Community Rescue Service has been conducting searches along the Braid River in the County Antrim town.
The Police Service of Northern Ireland (PSNI) said Ms Mitchell was seen on CCTV walking in the direction of James Street at the weekend.
Police are continuing their investigations alongside search and rescue teams.
At the scene: Kevin Sharkey, BBC News NI reporter
Part of a housing block remains sealed off in James street.
There has been a police presence outside and a forensic operation inside the police cordon this morning.
Investigating teams are also carrying out enquiries along the street.
Elsewhere, searches are continuing along a stretch of the river Braid.
Ch Insp Arnie O’Neill said officers were “becoming increasingly concerned” as to her whereabouts.
“Chloe was wearing a green and black The North Face-style jacket, a white t-shirt, leggings and Nike trainers,” he said.
“A 26-year-old man has been arrested in Lurgan this afternoon and is currently helping police with enquiries.”
On Thursday night, Community Rescue Service teams gathered along the banks of the Braid River while others searched in the river itself.
Regional Commander Sean McCarry spoke to BBC Good Morning Ulster on Friday.
Wide-ranging search
“Our teams were using special equipment to assist with the search,” he said.
“We started yesterday morning in the early hours and went right through into this morning.
“The search is quite wide ranging. The focus, of course, is in the last place where Chloe was seen.
“Our teams are working along the Braid River. Because it has been so dry through the past few weeks there isn’t a big flow in the river.
“We are not searching on the basis that we think Chloe might have got into difficulties in the river; we are searching on the basis of it is within the vicinity of the search area.
“We concentrate on all waterways and all areas as we carry out the search.”
Mr McCarry said a large number of people involved is involved in the search.
“We have about 35 people on the job this morning. We expect that to increase throughout the day.”
In a social media post, K9 Search and Rescue said its team had assisted in the search for Ms Mitchell in the Harryville area of Ballymena.
A spokesman said the teams had been conducting searches and had covered an extensive area.
He said the teams would remain in place and continue searching until they are told they are no longer needed.
The PSNI appealed for anyone with information to contact them by phoning 101.