Jeremiah 51:32

And that the passages are stopped, and the reeds they have burned with fire, and the men of war are affrighted.

Passages are stopped - the guarded fords of the Euphrates are occupied by the enemy (note, Jeremiah 50:38).

The reeds ... burned - "the reeds" [ haa'ªgamiym (H98)], literally, the marshes. After draining off the river, Cyrus "burned" the stockade of dense tree-like "reeds" on its banks, forming the outworks of the city fortifications. The burning of these would give the appearance of the marsh or river itself being on "fire."