By Dean Meminger
Police Commissioner James O’Neill tweeted photos showing the device which was stored inside a plastic bucket inside a supermarket freezer bag.
It happened during the morning rush at the Parsons Green station in Southwest London.
Passengers were evacuated, and authorities say more than a dozen people were injured.
None of the injuries are considered serious or life threatening.
Britain’s terror alert level has not been raised.
London Mayor Sadiq Khan says the incident will not change his city.
“These terrorists, these evil and cowardly individuals who want to divide us and disrupt our way of life. As the mayor of London I can say this and I can speak for Londoners – we are not going to allow them to do so,” Khan said.
President Donald Trump tweeted a response Friday morning, condemning those behind the attack as “loser terrorists”.