“Scores” of police officers are searching for a 22-year-old woman who went missing after a night out.
Brooke Morris, from Trelewis, Merthyr Tydfil, disappeared after being given a lift home from the town centre in the early hours of Saturday.
Police said Ms Morris’s disappearance was out of character and her family were going through a “dreadful ordeal”.
At least 100 people with dogs, as well as firefighters and workers, have joined the search.
Ms Morris was last seen at about 02:30 BST wearing a long-sleeved red top and jeans.
Supt Ceri Hughes from South Wales Police said: “We know that Brooke has been into Merthyr town centre with some friends who dropped her off near to her home address.
“The last confirmed sighting that we have of Brooke suggests that she didn’t actually go into her home and instead went down a lane that leads towards a bridge that goes into Treharris.”
Supt Hughes said the family were going through a dreadful ordeal, adding: “This is out of character for Brooke not to have any contact with her family now for a number of days.
“As you can imagine they’re absolutely devastated at Brooke’s disappearance and the fact that we haven’t heard from her since the early hours of Saturday.”
“They are desperate for news as to where Brooke is.”
Supt Hughes called the search a “large-scale policing operation”, with teams scouring the area as well as teams of investigators following up various lines of inquiry, adding “scores of officers” were looking for Ms Morris.
However, she said it was important to work with people to keep them safe while searching “densely overgrown areas and waterways and rail tracks”.
Police are keeping an open mind about what happened but have “no specific information” suggesting anyone else was involved.
“As the days pass and with no contact from Brooke, Brooke’s family and our concerns are growing increasingly for her,” she said.
“If Brooke is watching or hears this appeal, I would like to appeal to Brooke to make contact please with one of her family members or friends so that we can ensure she is safe.
Treharris Phoenix rugby club appealed for volunteers to help look for Ms Morris, following efforts by mountain rescue teams at the weekend.
Rosslyn Martin, 68, who was among the residents helping, said: “Everybody’s shocked and they just want to help and hope.”
The team’s clubhouse is being used as a focal point for the search, with snacks and supplies being provided by local businesses.
“We will coordinate a search of a specific terrain. You must be physically fit, have sound local knowledge of the area and be wearing appropriate clothing,” the club wrote on its Facebook page.
“If you think you can meet the above please join us at the rugby club for 10:30. We will require 40/50 fully equipped volunteers.
“The club will remain open as a central community coordination point until further notice.”
Councillor Sherelle Jago said the community support had already been “phenomenal”.
Councillor Ian Thomas added: “People are doing what they can because they’re very concerned. We can only hope for good news.”
Members of Central Beacons Mountain Rescue Team were searching for Ms Morris in the surrounding area over the weekend.