HOUSTON (AP) — Heavy storms slammed the Houston area again Friday, widening already dangerous flooding in Texas and putting stranded drivers and a school bus of children in need of high-water rescues. Officials redoubled urgent instructions for residents in low-lying areas to evacuate, warning the worst was still to come.

“This threat is ongoing and it’s going to get worse. It is not your typical river flood,” said Harris County Judge Lina Hidalgo, the top elected official in the nation’s third-largest county.

She described the surge of water as “catastrophic” and said several hundred structures were at risk of flooding. There had already been at least two dozen water rescues in the county, in addition to getting 30 pets to safety. Schools in the path of the flooding canceled classes and roads jammed as authorities closed highways taking on water.

For weeks, drenching rains in Texas and parts of Louisiana have filled reservoirs and saturated the ground. Floodwaters partially submerged cars and roads this week across parts of southeastern Texas, north of Houston, where high waters reached the roofs of some homes.

More than 11 inches (28 centimeters) of rain fell during a 24 hour period that ended Friday morning in the northern Houston suburb of Spring, according to the National Weather Service, which has issued a flood warning until Tuesday for the region.

In the rural community of Shepherd, Gilroy Fernandes said he and his spouse had about an hour to evacuate after a mandatory order. Their home is on stilts near the Trinity River, and they felt relief when the water began to recede on Thursday.

Then the danger grew while they slept.

“Next thing you know, overnight they started releasing more water from the dam at Livingston. And so that caused the level of the river to shoot up by almost five or six feet overnight,” Fernandes said. Neighbors who left an hour later got stuck in traffic because of flooding.

In Montgomery County, Judge Mark Keough said there had been more high-water rescues than he was able to count.

“We estimate we’ve had a couple hundred rescues from homes, from houses, from vehicles,” Keough said.

In Polk County, located about 100 miles (160 kilometers) northeast of Houston, officials have done over 100 water rescues in the past few days, said Polk County Emergency Management Coordinator Courtney Comstock.

She said homes below Lake Livingston Dam and along the Trinity River have flooded.

“It’ll be when things subside before we can do our damage assessment,” Comstock said.