The sealed-off Overtown neighborhood, scene of more unrest as angry blacks set fires and hurled rocks and bottles for a second day today, was reported quiet tonight after the black man whose shooting triggered the unrest died at a hospital.

Police in riot gear had blocked street entrances with patrol cars and fired tear-gas canisters in an effort to quiet the neighborhood, just north of downtown. One looter was killed in violence Tuesday night, nine other persons were injured and 29 were arrested.

At least 10 persons were injured in renewed trouble today, and police increased the cordoned-off area from 105 square blocks to 195 square blocks.

After the death at 6:45 p.m. of Nevell Johnson Jr., 21, police said streets remained quiet. Johnson was shot at a video arcade Tuesday night by a Hispanic policeman who said he thought Johnson had a gun.

City Manager Howard Gary said that a contingent of black police officers was sent to Overtown to maintain order and that a committee of 15 black community leaders was appointed to oversee the police presence.

"The leaders have been on the street talking to people and calming them down. We think considerable progress has been made," he said.

Gary ordered police to return because residents and business owners called to demand protection. Liquor stores and gas stations were ordered closed.

Three grocery stores were burned and looted Tuesday night, and a vehicle was rammed through the front door of a meat-packing company.

President Reagan, asked in Palm Springs, Calif., about the rioting, said, "I just don't think there's any room for that, for violence in the streets." Aides said White House staff members had been in contact with officials in Miami.

In Washington, Associate Attorney General Rudolph W. Giuliani said the FBI will investigate Johnson's shooting. The probe, to be reviewed by the Justice Department's Civil Rights Division, is being undertaken at the request of the Miami police and the Florida chapter of the NAACP, he said.

Johnson died of respiratory complications after surgery for a bullet wound. The two officers involved in the incident were relieved of duty, with pay, pending an investigation. Johnson had been charged with carrying a concealed .22-caliber handgun, police said.

"I want the truth and, when I get the truth, they're going to pay," said Johnson's father, Nevell Johnson Sr. "I don't want no violence. All I want is the officer to be punished, and I will see that he is punished."

Miami police Chief Kenneth Harms said the shooting occurred after two Hispanic officers entered to check for drug dealing. He said one of the officers noticed a bulge in Johnson's pocket that appeared to be a gun.

Harms' report said that Officer Luis Alvarez put his hand on the bulge and that "the officer's gun discharged," hitting Johnson in the neck.

Jeffrey Hoskins, a friend of Johnson standing next to him when he was shot, said Johnson "never had time to say a word. They just grabbed him and spun him around and shot him."

Hoskins and other witnesses gave their accounts at an emotional community meeting with Gary that erupted into a shouting match today. Gary had ordered police out of the area but, by this afternoon, police ordered road barriers back in place.

Of 29 arrested in the violence, 23 were charged with burglary and the others with crimes including aggravated battery, loitering, carrying a concealed firearm, possessing stolen property and attempted arson.

Three police cars and two journalists' cars were burned.