Water searches are underway as part of investigations into the missing 22-year-old Brooke Morris from Merthyr Tydfil, who disappeared in the early hours of Saturday morning.
Police say she has not been seen since she was given a lift home by people known to her on Friday night after going out with friends in Merthyr Tydfil town centre.
Officers believe that Brooke did not actually enter her house, but her next movements are unknown.
Searches got underway on Sunday but by Monday morning police said they were growing "increasingly concerned for her welfare".
Specially trained officers are now continuing their search which they are focussing in the Trelewis and surrounding areas, including in and around local waterways and woods.
Family friend Richard McLean has been helping coordinate the search effort.
"She's a really nice girl. We are all worried sick", he said.
Brooke is described as 5ft 3” tall, slight build with long dark hair and was last seen wearing boyfriend style jeans and a red long sleeve top at around 2:40am on 12 October.
Many have been using social media to appeal for information on Brooke's whereabouts, who plays for women's rugby team Nelson RFC Belles.
The Welsh Rugby Union tweeted the appeal to find her, and the rugby club tweeted, "Please please help us find Brooke. She still hasn't been found yet and we just want her home safely to all her family & friends!
"Further, we like to say a massive thank you to all the emergency services for your support in searching for Brooke."