At least 20 girls are missing from an all-girls Christian summer camp in South Texas after catastrophic floods struck the area in the wake of severe overnight storms.

At least 24 people were dead and many missing after torrential rains unleashed flash floods along the Guadalupe River in Texas.

Texas Lieutenant Governor Dan Patrick said authorities were searching for 23 girls listed as unaccounted for among more than 700 children who were at a summer camp when it was swept by floodwaters.