A spokesman for the company managing the building has so far refused to confirm who was responsible for the defect.
Following the revelation of responsibility, the facilities management firm has also decided to reopen the plaza at the tower's base. It had been closed since the window dived to the ground in the early hours of 18 April.
The investigation into the fault was conducted under extremely secret conditions and this remains the case - none of the parties involved, including Foster and Partners, will comment on these early findings.
At this stage it is unclear whether the investigation has stretched to checking all 6,000 glass panels in the landmark's facade.