Baltimore: 'Mass casualty event' as bridge hit by ship collapses into ...

We've just been hearing from Ian Firth, a structural engineer and bridge designer.

He says a heavy ship like the Dali will impart a very large load of many thousands of tonnes when it hits something solid, such as a bridge support.

"The support is a very, relatively, flimsy structure when you look at it, it's a kind of trestle structure with individual legs", he says. "So, the bridge has collapsed simply as a result of this very large impact force."

The vessel should have been going, of course, down the centre of the channel some 350 metres (1,150ft) wide, Firth says, "but for whatever reason it must have strayed off and has hit the support".