An investigation began today after a senior police officer admitted changing evidence during the Jean Charles de Menezes inquest.
The Special Branch officer, named only as Owen, deleted a line in his computer notes which claimed Deputy Assistant Commissioner Cressida Dick initially said the Brazilian electrician could "run onto Tube as not carrying anything".
But today he told Mr de Menezes's inquest: "On reflection, I looked at that and thought I cannot actually say that."
Ms Dick was the officer in charge of operations when the Brazilian electrician was shot.
An Independent Police Complaints Commission said: "This matter will be subject to an investigation and we are not in a position to comment further at this stage."
The investigation comes as a senior detective claimed he "cannot recall" whether police discussed photographs which could have stopped officers mistaking Mr de Menezes for a failed suicide bomber.
The 27-year-old was shot dead by police in London in 2005 after they mistook him for a suicide bomber after boarding a train at Stockwell Tube station.
The hearing continues.