If you come across anything treat it with extreme care.
Back in the 70s, clearing overgrowth in the garden, I came across something labelled "Smoke float, to dispose pierce (X) and drop in deep water". It had not been pierced so I called the local police. They looked at it, told me they had once put a similar one in the car and it had started smoking, so they called the bomb disposal people.

It turned out to have been opened on the lower side once the bomb squad had dug it out and turned it over!

However, that was only a maritime distress signal implement and the bomb squad insisted that the right course of action had been taken, so don't risk things.

Robin