A major dam outside Houston has begun spilling over as Storm Harvey pushes the reservoir past capacity, a Texas official says.
Engineers have tried to prevent nearby communities from being inundated by releasing some of the water held by the Addicks dam.
But flood control official Jeff Lindner says water levels are now over the height of the reservoir edge.
Harvey has brought huge floods to Texas and is starting to affect Louisiana.
Unprecedented rainfall has forced thousands of people to flee their homes. At least nine people are reported to have died in the Houston area.
Donald Trump is headed to Texas with First Lady Melania Trump to survey the damage, much of which can not be assessed until rainfall stops.
