A man was arrested in Birmingham last night by detectives investigating the murder of Mary-Ann Leneghan.
The 19-year-old was taken into custody an hour after an 18 - year- old was arrested in London as part of the same investigation.
The 16-year-old and her 18-year-old friend, who remains seriously ill in hospital, were abducted by a gang of six men in Reading, Berkshire, late on Friday night.
Det Superintendent Mark Warwick, of Thames Valley Police, who is leading the investigation, said the arrests marked a "significant" development.
A 21-year-old man arrested on Tuesday remains in custody and is still being interviewed.