A man has been arrested in connection with the disappearance of university student Joy Morgan.
Police described the search for Ms Morgan, who was last seen in Ilford, east London, on December 26 as "complex”.
The Hertfordshire University student, of Hatfield, Hertfordshire, was reported missing on February 7.
A 40-year-old man from London has since been arrested and released on bail while inquiries continue.
Tuesday was Ms Morgan's 21st birthday.
She is black, of slim build, around 5ft 5in tall, with black afro-style hair which she often covers with a scarf. She also wears glasses.
Her family issued an appeal, saying: "We love you, we miss you. Wherever you are, text or call so that we know you are alright.
"It doesn't matter what has happened, just come home."
Ms Morgan has links to Ilford, Battersea and Cricklewood in London, as well as Bedfordshire.
Welwyn Hatfield Chief Inspector Tannis Perks said: "This is a complex missing person investigation and we are working hard to establish the circumstances surrounding Joy's disappearance.
"Understandably her family are extremely worried about her and are desperate to know that she is OK. I would like to appeal to Joy to get in touch to let us know that she is safe.
"If you have information about Joy's whereabouts please get in touch on 101. For immediate sightings, call 999 straight away."
