The woman charged in connection with the deaths of the schoolgirls Holly Wells and Jessica Chapman was put on suicide watch after prison officers found cuts on her wrist.
Maxine Carr, 26, was put under special guard after cuts on her left wrist were noticed on 25 May. The cuts were discovered when warders were called to her cell in Holloway prison. She was taken to Holloway's health centre, where her wounds were treated but did not need stitches.
Two weeks later her boyfriend, Ian Huntley, who is accused of the murders of the 10-year-olds, was taken ill with an overdose. Mr Huntley, of Soham, Cambridgeshire, was taken to Milton Keynes General Hospital on 9 June from the high-security Woodhill prison, Buckinghamshire.
The cuts on Ms Carr's wrist were believed to be caused by "self-harm" and described as superficial. She was put on suicide watch for 10 days after the incident at Holloway prison, north London, where she is on remand awaiting trial.
The Prison Service said that it could not comment.
The schoolgirls disappeared from Soham, Cambridgeshire, last August. They were found dead two weeks later.
Ms Carr, also of Soham, Cambridgeshire, pleads not guilty to two charges of assisting an offender and one of conspiring to pervert the course of justice. Mr Huntley has admitted conspiring to pervert the course of justice but denies murdering the girls.