A large blast in the Lebanese capital, Beirut, has killed at least 50 people and injured more than 2,700 others.

Officials are blaming highly explosive materials stored in a warehouse for six years.

President Michel Aoun tweeted it was “unacceptable” that 2,750 tonnes of ammonium nitrate was stored unsafely.

An investigation is under way to find the exact trigger for the explosion. Lebanon’s Supreme Defence Council said those responsible would face the “maximum punishment” possible.

Australian Prime Minister Scott Morrison said at least one Australian has been killed in the Beirut blast and the Australian Embassy building has been “significantly compromised.”

While it is not clear what caused the explosion, tensions in Lebanon are high at this time, ahead of the verdict in a trial over the killing of ex-PM Rafik Hariri in 2005.