LONDON  The newspaper vendor who died after being struck by a police officer during the Group of 20 summit meeting earlier this month was killed by abdominal bleeding and not by a heart attack, according to an independent autopsy whose conclusions were released Friday.

This flatly contradicts earlier assertions by the police, who maintained that the newspaper vendor, Ian Tomlinson, died of a heart attack. It also opens the door for possible manslaughter charges against the officer who attacked Mr. Tomlinson, pushing him and striking him from behind with a baton, shortly before he collapsed.

The Independent Police Complaints Commission, which is investigating the incident, said that because of the new autopsy, the officer in question had been “interviewed under caution for the offense of manslaughter.” That means that the officer, whose name has not been released, has been formally interrogated but not charged with a crime.

Mr. Tomlinson died April 1 in London’s financial district during protests against the Group of 20 meetings. He was trying to walk home from work and was not part of the protests.