A tornado has swept through a city on the US-Mexico border, killing at least 13 people.
Rescue workers began digging through the rubble of damaged homes in Ciudad Acuna, a city of 125,000 across from Del Rio in Texas in a race to find victims.
Ten adults and three infants died when the tornado hit a seven-block area which Victor Zamora, interior secretary of the northern state of Coahuila, described as "devastated".
Hundreds of people were treated at local hospitals, authorities said, and as many as 800 homes had been destroyed, with thousands more damaged.
"There's nothing standing, not walls, not roofs," said Edgar Gonzalez, a spokesman for the city government, describing the worst affected square mile.
Photos from the scene showed cars with their bonnets torn off, resting upended against single-storey houses. One car’s frame was bent around the gate of a house. A bus was seen flipped and crumpled on a road.
The tornado struck not long after daybreak, around the time buses were preparing to take children to school, Mr Zamora said.
In Texas, 12 people were reported missing after the holiday home they were staying in was swept away by rushing floodwaters in a small town popular with tourists.
A line of storms that stretched from the Gulf of Mexico to the Great Lakes dumped record rainfall on parts of the US plains and midwest, spawning tornadoes and causing major flooding that forced at least 2,000 Texans from their homes.
The storms were blamed for three deaths on Saturday and Sunday, including two in Oklahoma and one in Texas, where a man's body was recovered from a flooded area along the Blanco River, which rose 26ft in an hour and created huge piles of debris.
Texas governor Greg Abbott flew over parts of the Blanco yesterday, a day after heavy rains pushed the river into surrounding neighbourhoods.
He said the storms had “relentless tsunami-type power”, and urged communities downstream to monitor flood levels and take the threat seriously.
The governor added 24 counties to his disaster declaration, bringing the total to 37, most in the eastern half of the state.
Among the worst-affected communities were Wimberley and San Marcos, along the Blanco in the corridor between Austin and San Antonio.
About 1,000 homes were damaged throughout Hays County. Five police cars were washed away, and the fire station was flooded, said Kristi Wyatt, a spokeswoman for San Marcos.
Rivers swelled so quickly that whole communities awoke on Sunday surrounded by water. The Blanco crested above 40ft — more than triple its flood stage of 13ft. The river swamped Interstate 35 and forced parts of the busy north-south highway to close. Rescuers used pontoon boats and a helicopter to pull people out.
Hundreds of trees along the Blanco were uprooted or snapped, and they collected in piles of debris 20ft high.
A tornado briefly touched down on Sunday in Houston, damaging rooftops, toppling trees, blowing out windows and sending at least two people to hospital. Fire officials said 10 apartments were heavily damaged and 40 others sustained lesser damage.
Dallas faced severe flooding from the Trinity River, while the Red and Wichita rivers also rose far above flood stage.