The fire had dwindled to almost nothing, but its smoke was thickening.

The smoke thinned for a while, then thickened again.

Slowly the smoke over the offending tree thickened and the formation's motion slowed.

The smoke thickened suddenly and a distant crackling could be heard.

The smoke thickened and the cat could see only shadow in the room.

The smoke was thickening, the deadly fire taking hold.

We stood locked in this horrifying vignette as the smoke around us thickened.

I could see none of the flames myself, but gradually the smoke was thickening.

The torch was burning low and the smoke was thickening.

They were unmarked though the smoke was thickening all round us.