SHREVEPORT, LA., SEPT. 21 -- Heavily armed police sealed off a 12-block area tonight after hearing sporadic gunfire in a riot-scarred neighborhood where a white woman allegedly shot a black man to death 24 hours earlier.

No injuries or serious damages were reported tonight, and there were no arrests immediately reported in Louisiana's third-largest city.

The white woman is accused of murder in Tuesday night's shooting, and six blacks were arrested during the rioting that followed, police said.

Mayor John Hussey said the strategy tonight was to wait out troublemakers. "The idea is to seal off the area," he said. If you seal it off, don't let any cars through, then there's nothing for them to throw at."

Although the atmosphere was tense, Police Chief Charles Gruber said it was nothing like what the city faced after Tuesday's rioting.

Tonight's violence occurred hours after black leaders called for Cedar Grove residents to stay calm and guard against a recurrence of the burning and looting late Tuesday night and early today.

"We're sitting on a powder keg," said state Rep. Alphonse Jackson, who called for formation of a biracial anticrime committee. "People want protection. I call on citizens to restore law and order."

In the Tuesday rioting, there were reports of racial slurs and chants of "Hot Biscuit," the restaurant where a white teen-ager killed a black teen-ager Aug. 4, an incident that set off racial tension here.

Hussey and Gruber said at a news conference earlier today that the sparks for the Tuesday riot were the two shootings, but both said there were deeper causes.

"We've got problems in our economy; we've got problems in our racism; we've got many other problems," said Hussey, adding that drinking and a soured drug deal preceded Tuesday's shooting.

The Tuesday night crowd reached 1,000 people at its peak, Gruber said, but other police estimates said the total was 300 to 500 most of the time. A seven-block area was cordoned off.

Rather than quell the disturbance, Gruber let it run its course. "If Gruber had moved into the area, we would have had a large number of people hurt, so I commend him for it," Jackson said.

The Tuesday outbreak was triggered by the fatal shooting of a black man identified as William David McKinney, 20, who lived in the Cedar Grove neighborhood.

A white 17-year-old from Greenwood was booked on a charge of second-degree murder, Police Cpl. E.T. Rushing said. A second woman was questioned but not charged.

A man who identified himself only as a cousin of McKinney's said McKinney was shot at random after a woman trying to buy cocaine from a group of men was robbed. When they ran with her purse, she "took out her frustration" on McKinney, he said.

Officers said people in a convenience store tried to detain the woman until police came, but a crowd of blacks gathered outside and began throwing bricks at the business and at passing motorists who were white.

A witness, Anthony Johnson, said that after police took the woman away, the crowd doused the store with lighter fluid, set it afire and went on a rampage. The building, containing the store and a liquor shop, was destroyed.

Patients and workers at Eden Gardens Nursing Center, across the street, watched the burning and looting.

"Some of the guys had so much stuff in their bags they couldn't walk," said Betty Truett, a nurse.

In the Aug. 4 shooting, five white men were arrested and one admitted the shooting, saying he was defending himself. He is being held on $250,000 bond on second-degree murder charges. Charges against three of the others were dropped in return for their cooperation.

The shooting enraged Shreveport's black community, but calm prevailed when black ministers exhorted congregations to let police handle the investigation.