Kokulavathani Mayuran, 31, was last seen in Gloucester at around 11pm on Tuesday and was reported missing to police at around 10.15pm, two days later.
Earlier, police said they had arrested a 31-year-old man on suspicion of murder.
But Detective Superintendent Simon Atkinson has now confirmed the man had been released.
He said: “Following further investigation we believe this to be a missing person inquiry.
“As a result the 31-year-old Gloucester man, who was arrested in connection with her disappearance, has been released without charge.
“We are still extremely concerned for Kokulavathani’s welfare and we would urge anyone who sees her or knows where she is to contact us immediately.”
Kokulavathani is originally from Sri Lanka, she is described as being around 5ft 4in with a heavy build.
She has long dark hair and it is thought she could have been wearing a long black coat.
People with information on her whereabouts are asked to contact police via the 101 number. (UKPA)