There are apparently at least three breaches:
Dozens of blocks in the Ninth Ward were under water as a waterfall at least 30 feet wide poured over and through a dike that had been used to patch breaks in the Industrial Canal levee. On the street that runs parallel to the canal, the water ran waist-deep and was rising fast. Guidry said water was rising about three inches a minute...
Sally Forman, an aide to Mayor Ray Nagin, said officials knew the levees were compromised, but they believe that the Ninth Ward is cleared of residents.
"I wouldn't imagine there's one person down there," Forman said.
Mitch Frazier, a spokesman for the Army Corps of Engineers, said contractors were being brought in Friday morning in an effort to repair the new damage. The corps had earlier installed 60-foot sections of metal across some of the city's canals to protect against flooding and storm surges...
There's more in "New Orleans' 9th Ward floods":
...CNN photojournalist Alfredo DeLara echoed his observations. "We're talking 5 to 10 inches in the one to two minutes we were standing in this one spot," he said. "There's nothing stopping that water from just pouring in."
"The Army Corps of Engineers placed a lot of sand here with helicopters, with earthmoving equipment, and tried to shore it up. But it looks like it didn't hold," he said...
Oddly enough, that appears to have replaced an earlier CNN report (apparently no longer on CNN's site) that included the following now missing bit:
Nagin expressed confidence that the levees would hold.
"The Army Corps of Engineers has done some work to assure us that they can handle that type of storm surge in the current condition at our levees," Nagin told reporters.