Flooding in Houston historically at its worst

Floodwaters that inundated Houston, bringing the city to a standstill, were blamed Tuesday for at least five deaths, and statewide the disaster claimed at least 12 lives, authorities said today.

Houston Mayor Annise Parker did not identify the fatalities, but said that two were found inside vehicles and another was found in a bayou and police suspect that the individual suffered from a heart attack while trying to push their vehicle.

A fourth person was also found in a bayou, and officials said it is possible he was a man who was lost during a rescue attempt earlier today. Another man had a heart attack trying to push his car out of flood waters.

"Given the magnitude and how quickly it happened, in such a short period of time, I've never seen this before," said Rick Flanagan, Houston's emergency management coordinator.

There are still 30 people unaccounted for in Hays County, according to the latest figures from a Texas Department of Public Safety spokesperson.

"We have a thousand properties that have been visually inspected. We believe that there are as many as 4,000 with significant damage," Parker said this afternoon.

Overall the storms and flooding were blamed for 15 deaths since Friday, including four people who were killed in Oklahoma. Another 13 were killed in a tornado that touched down Monday in Ciudad Acuna, a Mexican town on the border with Texas.

Among the dead was Alyssa Ramirez, a homecoming queen and student council president who was driving home Saturday night from her prom in the small town of Devine southwest of San Antonio when she got stranded in high water. She called 911 and even called her father, but the flood waters rose too fast for her to be rescued.

Some of the underpasses in Houston that flood in normal rainfalls were the first areas affected when 6 to 11 inches of rain fell by early this morning. Parker said there have been more than 2,500 cars left stranded on highways and roadways.

Parker explained the rain created two problems: the first being that the ground was largely saturated and couldn't absorb all of the evening's rainfall because of "several weeks of really heavy rainfall." On top of that, the small rivers that surround and run through Houston began overflowing their banks and flooding neighborhoods.

"It's still a dangerous situation along the bayous, they're flowing very, very rapidly," Parker said.

A city official noted that they responded to 968 incidents overnight, 531 of which were water-related.

Article by Rachel Katz, Dan Good and Meghan Keneally via Good Morning America