Police said a man who bombed a London train bought the parts online. They said a refugee left the bomb on a crowded subway train. It exploded during rush hour at 8.20am. About 30 passengers had burns. Police said the bomb didn't work properly. It had knives, screws, glass and other dangerous things inside it.

The bomber bought many things from Amazon. He bought an explosive called TATP. It is very powerful. Police said the bomber wanted "maximum destruction". Reporters said Amazon's site showed visitors other things that could make bombs. Amazon said it will make sure its products are presented in a better way.