For 16 critical hours, Federal Emergency Management Agency officials, including then-Director Michael D. Brown, dismissed urgent eyewitness accounts by FEMA's only staffer in New Orleans that Hurricane Katrina had broken the city's levee system the morning of Aug. 29 and was causing catastrophic flooding, the staffer told a bipartisan Senate panel investigating the response to the hurricane.

Marty Bahamonde, sent to New Orleans by Brown, said he alerted Brown's assistant shortly after 11 a.m. that Monday with the "worst possible news" for the city: The Category 4 hurricane had carved a 20-foot breach in the 17th Avenue Canal levee.

Five FEMA aides were e-mailed Bahamonde's report of "water flow 'bad' " from the broken levees designed to hold back Lake Pontchartrain. Bahamonde said he called Brown personally after 7 p.m. to warn that 80 percent of New Orleans was underwater and that he had photographed a 200-foot-wide breach.

"FEMA headquarters knew at 11 o'clock. Mike Brown knew at 7 o'clock. Most of FEMA's operational staff knew by 9 o'clock that evening. I don't know where that information went," said Bahamonde, a 12-year veteran of the agency who has worked full time since 2002 as a public affairs official.

Bahamonde said his accounts were disregarded by FEMA officials in Baton Rouge, La., and at the agency's headquarters in Washington amid conflicting information.

Bahamonde also said he found it "amazing" that New Orleans officials continued to let thousands gather at the Superdome, even though they knew that the area around it was going to get flooded. Ten people later died in the stadium.

-- Spencer S. Hsu

Staffer Marty Bahamonde says he told FEMA headquarters about the flooding.