Arsema Dawit had to wait 12 days for police to make contact after complaining that an alleged stalker had threatened to kill her.

Scotland Yard yesterday ordered an internal investigation into the actions of officers in the weeks leading up to the stabbing of the schoolgirl as she returned home on Monday.

The inquiry will focus on whether officers could have saved Arsema, who was found stabbed to death in a lift at the flats where she lived near Waterloo station, Central London.

The Times has learnt that Arsema and her mother gave police the name of a suspect who had assaulted and threatened to kill her, although it is not known whether she gave them the correct one.

The teenager, who sang in the choir at her local Eritrean church and celebrated her 15th birthday on Saturday, described the suspect as being aged 29 or 30. A man was arrested shortly after the killing in “an agitated state”. Although he is 21, police are confident that he is the suspect from the original inquiry.

The schoolgirl had gone to Kennington police station with her mother on April 30. She told officers that a man had assaulted her and threatened to kill her at a nearby McDonald’s restaurant on April 16.

The matter should have been dealt with quickly because it involved a young person, categorised by the police as being vulnerable.

The case was given to Southwark CID but it was not until May 12 that a Safer Schools officer spoke to the victim at her school, Harris Academy. However, Arsema denied any knowledge of the incident. A week later police contacted her mother and the inquiry was continuing when Arsema was killed.

A spokesman for Scotland Yard said: “The victim was unaware of the incident and had no knowledge of it. Despite this we continued to investigate the circumstances of the incident and Arsema’s mother was subsequently contacted on May 19.

“The investigation was being progressed when Arsema was tragically killed.”

He added: “It has been established that Arsema and the suspect knew each other but the exact nature of their relationship is unclear at this stage.”

Detectives from the Territorial Policing Violent Crime Directorate have started an internal review and part of their investigation will focus on what officers were doing for the 12 days before they visited the schoolgirl.

Times Recommends

• How I lost the gift of joy for a while
• Why Ann Widdecombe has got it wrong
• Alas, it’s the end of the road for petrolheads