Footage showed Mr Tomlinson being shoved by an officer - video courtesy Guardian.co.uk
A police officer thought to be shown on video pushing a man at the G20 protests in London who later died is to be questioned by the police watchdog.
An independent criminal probe has begun into the death of Ian Tomlinson, 47, who had a heart attack minutes after the incident on 1 April.
More video aired on Channel 4 appears to show him being hit with a baton.
The Metropolitan Police (Met) has now acknowledged Mr Tomlinson came "into contact with police" before he died.
Initially the force said it was unaware he had sustained the alleged assault and said its officers' first contact with him was when they gave him medical aid before he died.
"It is now clear that Mr Tomlinson did come into contact with police prior to his death and that a number of the officers depicted in the footage on a national newspaper's website have identified themselves as MPS officers," it said in a statement.
Scotland Yard said the officer seen on Channel 4 footage was one of four who had come forward to give information.
The IPCC has ordered a second post-mortem test as part of its inquiry.
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