NEW ORLEANS -- Don't go near the water in New Orleans.

That's still the advice from the Environmental Protection Agency, which says floodwaters there still pose a health risk because of dangerous levels of sewage-related bacteria and toxic chemicals. They aren't saying when the people will be able to live in the city again.

As for air quality, EPA officials said a minimal number of pollutants, such as methanol and freon, have been found, but that the levels don't worry them.

Water samples that were drawn on Sept. 4 and Sept. 6 turned up high levels of chemicals such as hexavalent chromium, arsenic and lead. An EPA spokeswoman calls the New Orleans flooding "one of the biggest environmental challenges in our agency's history."

More Criminal Charges May Be Filed Over Hurricane Deaths

There may be more criminal cases related to the rising death count from Hurricane Katrina.

Louisiana Attorney General Charles Foti said he will investigate every death at a nursing home or hospital that's not deemed to be from natural causes. And he said he won't hesitate to bring more charges.

The owners of a nursing home where 34 people died are free on bond after being charged with 34 counts of negligent homicide. Authorities said they turned down offers of rescue. Foti said it's "pathetic" they didn't evacuate.

The victims at Saint Rita's Nursing Home in Chalmette died Aug. 29, the day Hurricane Katrina hit.

Foti said that inaction by Salvador and Mable Mangano resulted in the deaths, and that Manganos were repeatedly warned to move patients. He said the Manganos had an evacuation plan but didn't act on it.

Foti said the owners had a contract with an ambulance service to evacuate the patients, but didn't call the company. And he said they also turned down an offer from Saint Bernard Parish offici als, who asked if the nursing home wanted help evacuating.

But their lawyer, Jim Cobb, said the Manganos had to make a difficult decision between evacuating the patients, many of them elderly and on feeding tubes, or keeping them at the home and weathering the storm. He said the owners were there and "saved 52 lives."

Cobb said guilt is far from clear cut. He said a mandatory evacuation never came

Tom Rodrigue, a man whose mother died at the nursing home, said she deserved better than to "drown like a rat."

The husband-and-wife owners have been charged with negligent homicide in the deaths. Foti said, "They had a duty and a standard of care to people who could not care for themselves."

Over the weekend, more than 40 bodies were pulled from a flooded New Orleans hospital. Louisiana's attorney general said the two were repeatedly warned to leave.

So far, Louisiana official have confirmed 423 Katrina deaths for a five-state total of 659.

Authorities said more victims may be found as the water recedes. An Oklahoma National Guard officer said "everything is driven by the water."