A major search and rescue operation is continuing through the night in Texas after flash floods killed at least 24 people and left many girls missing from a Christian summer camp.

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.

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.