London was hit by a terrorist attack on Friday morning when a crude device exploded on a Tube train at Parsons Green station.
Passengers reported an explosion in a carriage of the train shortly after 8 a.m., during the morning rush hour. Several people appeared to have burn injuries.
Health officials say the number of people injured in the bombing is now at 22. None of the injuries is thought to be serious or life-threatening.
According to Terrorism analyst Magnus Ranstorp with the Swedish Defense University, Londoners have been very fortunate because the bomb placed on a subway appears not to have fully detonated.
British police say no one has been arrested in connection with a bombing on a London subway train, but hundreds of detectives are at work trying to hunt down the perpetrator or perpetrators.
London has been targeted by attackers several times this year, with vehicle attacks near Parliament, on London Bridge and near a mosque in Finsbury Park in north London.