ATLANTA (AP) _ A package holding what appeared to be a tear-gas bomb was mailed to the Southeastern regional headquarters of the NAACP and spewed gas throughout an office building when it was opened Monday, injuring eight people.

Civil rights leaders denounced the attack as apparently racist. Federal officials said they will investigate to see if civil rights violations were involved.

A caustic gas ''similar to tear gas'' spread from the NAACP office through air-conditioning ducts into surrounding offices in the two-story building just southwest of downtown Atlanta, said Assistant Fire Chief Walter Campbell.

The eight injured people, taken to two downtown hospitals, included a 4- month-old infant and a 12-year-old. No one was seriously hurt, said officials at Grady Memorial Hospital and Georgia Baptist Medical Center. At least five of the injured were able to go home within a few hours.

Two staff members in the National Association for the Advancement of Colored People office when the bomb went off, Regional Executive Director Earl T. Shinhoster and secretary Murlene Murray, fled and were not seriously hurt, apart from burning eyes and throats, Ms. Murray said.

''This is just a terrible experience,'' she added. ''We've never experienced anything like this before in the 20 years I've worked here.''

''This is a very evil and dastardly act,'' Shinhoster said. ''I don't know why anyone would want to try to hurt innocent people like this.''

The package, ''no bigger than a hat box,'' arrived via Postal Service ''Priority Mail,'' Shinhoster said. It was addressed to the NAACP and not to anyone in particular.

The return address listed a law office and a location, ''but I'm sure it was fictitious,'' Ms. Murray said. She did not recall a specific name on the return address.

Shinhoster said he and Ms. Murray opened the package just after noon and immediately saw sparks. Two loud pops were then heard and a cylinder in the package began emitting a white-yellow caustic smoke, Shinhoster said.

The package remained largely intact.

Officers from the Postal Service, the FBI, city police and the city Fire Bureau arson squad were investigating, Campbell said.

''We'll be looking to see what jurisdiction, if any, we've got,'' said FBI agent Diader Rosario. ''Our interest is from the point of view of civil rights.''

Mayor Andrew Young urged city employees to be careful when handling any mail that might look suspicious.

U.S. Rep. John Lewis, D-Ga., was in the neighborhood speaking to a community group when he heard about the incident and went to the scene.

''Anytime something like this would come to the NAACP office, you have to believe it's racially motivated,'' said Lewis, a veteran of the civil rights movement.

''I think there's a climate existing in America now,'' he said. ''Twenty- five years later the seeds of racism are raising their ugly heads again.''