(Reuters) - White students at a Mississippi high school tossed a rope around the neck of a black student and pulled it tight like a noose, the NAACP said on Monday, asking federal authorities to investigate the incident as a hate crime.

The NAACP made its plea at a news conference with the black student's family, saying the student's mother was discouraged from filing a police report after the Oct. 13 incident and the school district has not officially informed the family of any disciplinary action taken against the white students.

Stone County School District superintendent Inita Owen declined to comment on the incident, saying she would not discuss a student discipline matter with the media.

"I can assure everyone that the Stone County School District takes all matters involving students very seriously and will do everything within its power to make sure that all policies and procedures were adhered to and that all of its students have a safe place to receive an education," she said in a statement.

Several of the white students have continued to attend Stone High School, along with the black student, said Derrick Johnson, president of the state branch of the National Association for the Advancement of Colored People.

He said the family was told off the record that one student was placed in an alternative setting. As many as four students are accused in the incident.

"This type of behavior should not be tolerated," Johnson said at a news conference webcast online. "These incidents should not be swept under the rug."

The student's mother stood by his side but did not comment. Stone High School is about 40 miles (64 km) north of Biloxi in southern Mississippi.

A spokesman for the Federal Bureau of Investigation in Jackson, Mississippi, said it was aware of the situation in Stone County. He would not confirm or deny whether an investigation was under way.

Reuters was unable to confirm with local law enforcement that the mother attempted to file a report.

Johnson said the white students involved had earlier this year come to school displaying Confederate flags from their vehicles. Many see the flag associated with the pro-slavery southern states during the U.S. Civil War as a racist symbol.

(Reporting by Letitia Stein in Tampa, Florida; Editing by Lisa Shumaker and Bill Rigby)