The public have been warned to avoid a 12-mile stretch of the canal network.

Let's take you to Jo Black, who is there for us.

Jo, what happened?

We're not quite sure at the moment.

The investigation into what happened is ongoing, but a major incident has been declared.

And as you can see behind me, there are police here, there are people who've been walking around in high visibility jackets.

Just over the road, there is some police tape.

It's across the entrance to the canal and the towpath, meaning people can't go down towards the canal.

And if you just look down there, you can see dead fish in the water.

It's just a rough estimate, but we think we can see around 100 fish from here.

And obviously, there will be others reported elsewhere along the canal.

The spill, the toxic spill, we are told was discovered on Monday.

As I say, an investigation is ongoing and we believe water testing is taking place.

Some of the people in high visibility jackets that we saw, one of them did have a very long pole with a metal beaker and another one was carrying something like a cool bag, something like that you put your sandwiches in on a very hot day.

So those water tests should be ongoing.

Results of those, we hope we'll find out soon.

The council leader, Walsall council leader Gary Perry, has confirmed the substance as sodium cyanide.

Now, we understand that chemical can cause seizures, vomiting and loss of consciousness.

And as you were just saying there, the public have been told to avoid a 12-mile stretch of the canal network, which runs from Walsall, where we are now, to Birmingham, but also taking in Wensbury, Tipton and West Bromwich.

Now, this chemical, we understand, is used in industry for things like metal cleaning, plating and photography.

It dissolves in the water and if you come into contact with it, it can be risky.

So it could be risky to people and their pets and anyone who is concerned has been told to contact the local NHS 111 or 999 if there is an emergency.

The authorities say they're working as cautiously and as quickly as they can and hopefully the restrictions will be reduced once they feel like they've got a grip on the situation.

Jo, thank you so much for updating us.