They said today that the floodwaters were 3.5 meters deep in some places, the highest in decades, and had swept away dozens of vehicles.
The officials spoke on condition of anonymity because they were not authorized to brief reporters.
Taiz has been the focus of heavy fighting between Shiite Houthi rebels and government forces, which are backed by a Saudi-led coalition.
The civil war has killed over 10,000 civilians. An outbreak of cholera has killed more than 2,000 people since late April.