The police department said Thursday it is investigating about a dozen officers suspected of looting during the lawlessness that engulfed the city after Hurricane Katrina (search).

News reports in the aftermath of the storm put officers at the scene of some of the heaviest looting, at the Wal-Mart in the Lower Garden District (search). Some witnesses, including a Times-Picayune reporter, said police were taking items from shelves.

"Out of 1,750 officers, we're looking into the possibility that maybe 12 officers were involved in misconduct," police spokesman Marlon Defillo said.

He rejected the use of the term "looting," and said authorities were investigating "the possibility of appropriation of nonessential items during the height of Katrina, from businesses."

Earlier this week, the city's police superintendent, Eddie Compass (search), resigned after weeks of criticism about the department's conduct during Katrina and its aftermath. On the same day, the department said about 250 police officers could face discipline for leaving their posts without permission during the crisis.

Meanwhile, business owners started streaming back into newly reopened sections of the city Thursday morning at Mayor Ray Nagin's (search) invitation, some vowing to rebuild, some saying they were pulling out.

The areas thrown open to business owners were: the French Quarter; the central business district; and the Uptown section, which includes the Garden District, a leafy neighborhood of antebellum and Victorian mansions. The neighborhoods escaped major flooding during Katrina.

Under the mayor's plan, residents of those neighborhoods will be allowed to return on Friday, a move that could bring back about one-third of the city's half-million inhabitants.

At Igor's, a pub and coin laundry in the Garden District, owner Halina Margan returned after Katrina and never left, despite Hurricane Rita's threat last week. She was ready to open for business on Thursday.

"It's lonely here. We need people," she said.

Blues music poured out the door of Slim Goodies diner, where by 10 a.m., owner Kappa Horn had already served pancakes, bacon and eggs over easy on plastic plates to more than 100 people.

"This is the first hot meal I've had in a month," said George Wichser, a Tulane University police officer who rode out the storm on campus.

Mary Russo parked her car in front of Shanty Too, her niece's boarded-up boutique on chic Magazine Street, and started to cry. Her niece could not bear to come, so Russo and other relatives were there to close the shop for good and bring anything salvageable to her other store closer to Baton Rouge.

"I just can't believe this has happened to the city," Russo said. "So much of this could have been avoided."

The mayor is pushing aggressively to reopen the city despite concerns raised by state and federal officials.

Serious health hazards remain because of bacteria-laden floodwaters, a lack of drinkable water and a sewage system that still does not work, said Stephen L. Johnson, chief of the Environmental Protection Agency.

"There are a whole lot of factors that need to be weighing on the mayor's mind," Johnson said.

He said the EPA was not taking a position on Nagin's plan. But he refused to answer when asked if he would allow his own family to return to New Orleans.

Federal officials said it would take at least another year to clean up all the hurricane debris in Louisiana.

Katrina's death toll in Louisiana rose to 923 on Thursday, up from 896 the day before, the state health department said.