Chemical incidents in the UK

In the UK most children are still off school for Summer.
This weekend is also a public holiday in most of the UK.

Recently there have been some "chemical incidents" mainly at beaches.

Today - [link to www.clactonandfrintongazette.co.uk (secure)]

11th August - [link to www.express.co.uk (secure)]

30th July - [link to www.bbc.co.uk (secure)]

2rd April - [link to www.express.co.uk (secure)]

They always seem to have unknown causes.