Police searching for a missing 21-year-old woman have said they are “increasingly concerned” for her safety.
Chloe Mitchell, who is described as a “high-risk missing person” was last seen in Ballymena on Friday night into the early hours of Saturday.
A 26-year-old man who was arrested in Lurgan in County Armagh is being questioned.
PSNI Supt Gillian Kearney said police were continuing their searches.
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.
“It’s out of character for her not to have contacted her family or friends,” said Supt Kearney on Friday afternoon.
“Her family are being supported by specialist but it’s a very worrying time,” she said.
“I hope she is safe and well and that’s why we are appealing for information and for the public to look at her photo and contact us if they have seen her.”
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.
“Chloe was wearing a green and black The North Face-style jacket, a white t-shirt, leggings and Nike trainers,” said Ch Insp Arnie O’Neill.
“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.
District Commander Darren Harper spoke to the BBC about the ongoing search.
Not easy terrain to search
“It’s a pretty significant operation whenever you take in the search areas,” he said.
Mr Harper said the river was not the only area being searched.
“We do have the water technical team in the water and [on] the river banks and we also have ground teams searching other areas,” he added.
He said difficult terrain, with dense shrubbery, brambles and steep river banks made the search difficult.
The hot weather also added to the challenge faced by personnel wearing waterproof gear, flotation devices and dry suits, he said.
“Currently we have around 20 to 25 members out on the ground. Yesterday there was around 50 to 60 members and there will be more volunteers that come throughout the day,” he explaned.
Asked if the Community Rescue Service had found anything significant, Mr Harper said: “We wouldn’t be doing our job right if we didn’t have some sort of finds. That’s then passed on to the police to find out if it’s relevant or not.”
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.
Another voluntary search and rescue group, K9 Search and Rescue, said in a social media post that its team had assisted in the search for Ms Mitchell in the Harryville area of Ballymena.
The PSNI appealed for anyone with information to contact them by phoning 101.