EYEWITNESS ACCOUNTS: The emergency cord was pulled and as the tube train drew into Oval station in south London a man dashed out of the doors and ran. Passengers in the smoke-filled carriage began to give chase but the man outran them and escaped through the station entrance.
Witnesses described how a flower seller outside Oval station had tried to catch him but failed. Paul Martin (32) said: "People started running out of the station. I saw a guy being chased. It was completely crazy. People were trying to drop him, to rugby-tackle him. There was a general melee."
Hugues Caillat, from France, had been buying a ticket in the station concourse when the man ran out. "Suddenly I saw a guy coming from the stairs," he said.
"He was running and at the same time people were running after him. I wanted to catch him but I was carrying heavy bags. The guy said something like 'what's wrong with these people'. He was a skinny Asian guy, with a little beard. He was about 19.
"The guy who sells the flowers was running after him as well. By chance the police were passing by. Both of us waved at them and shouted he's gone that way. Obviously something was wrong, otherwise what's the point of running?"
A witness in the carriage next to the one that contained the bag containing the device told Sky TV News: "All of a sudden there was a popping, it sounded like champagne popping. I didn't think anything of it at the time but then I heard a lot of shouting from the next-door carriage.
"People started saying, 'smoke, smoke'. One of the train guys came through and said 'Get off the train, we're evacuating, everyone out'.
"As we were walking past the carriage we could see the bag sitting on the chair. It was a big black rucksack, like the backpack-type ones that you get. When they got upstairs, people were really distressed. One lady was crying."
Ingrid Guyon, from France, was also in the next carriage. When it was evacuated she spoke to a woman who had been standing next to the man on the train when his bag exploded and smoke began to fill the carriage. The woman said the man had a backpack.
Ms Guyon said: "The bag exploded. We were evacuated in Oval. We were asked not to panic and just to leave. The guy ran away, people were trying to run after him.
"There was a terrible smell and a lot of people were shocked. They came running through into our carriage. I nearly fainted because of the smell. I was so scared. It was a terrible smell and there was lots of smoke. It was more like a smoke bomb."
After emptying the station police in protective suits entered to check for traces of chemicals. Sniffer dogs were brought to the scene. A half-mile cordon was set up around the station and surrounding streets, and residents were told to stay in their homes.