A train collision has killed at least four people and injured dozens in northern Egypt.Footage showed multiple overturned carriages and dozens of people surrounding them.One train was travelling from Giza to the Fayoum oasis, south west of Cairo, while the other was heading from Cairo to Aswan in the south.It is yet unclear what caused the accident but Egyptian President Abdul Fattah al-Sisi said an investigation was underway and would "hold accountable anyone who proves their negligence".Follow this story live.