TAX inspectors have been drafted in to help determine if the Spanish venue where four teenagers died was overcrowded.
An investigation has been launched into the tragedy, which was caused by a crowd surge during a Halloween party at the Madrid Arena on October 31.
Police claim 18,000 people were inside the venue at the time, despite the capacity being 10,600 and organisers insisting only 9,600 tickets were sold.
Inspectors will now try to calculate the number of tickets sold against the IVA (VAT) paid on the entrance stubs to determine the exact number.
The incident is thought to have been triggered by someone in the crowd throwing a firecracker which caused the crowd to stampede.
Speaking about the tragedy, Madrid Mayor Ana Botella said: “All Madrid residents, especially those of us who are parents, feel the profound sadness and grief the families of the victims are going through.”