The top of a hateful petition that circulated at a high school in Anne Arundel County, Md. (Copy of petition provided by Anne Arundel County schools)

Police have charged a 14-year-old girl with sending a tweet that included a threat to attack a Maryland school where students had circulated a white supremacist petition, authorities said.

The girl is accused of creating a Twitter account under the name @KoolkidsKlanKkk, reflecting the language used in a racist petition passed around this month at Arundel High School. Anne Arundel County police said she then posted a tweet on Jan. 9: “We’re planning to attack tomorrow.”

Anne Arundel Police Lt. Ryan Frashure said last week that authorities did not think the tweet represented a credible threat to the high school, but he said police were taking it seriously and launching an investigation.

Detectives worked with Twitter and a wireless service carrier, identifying the person responsible as an African American teenager who is a student at Arundel High. Police interviewed her in the presence of her parents, and she admitted to opening the Twitter account and sending the tweet, police spokesman Marc Limansky said.

She was charged on a juvenile citation with disruption of school activities, under state education law, and released to her parents, Limansky said. A large number of students did not attend school after learning of the threat, police said. Police have not publicly identified the girl because she is a minor, and The Washington Post generally does not identify minors charged with crimes.

The incident came after a petition circulated at Arundel High that described African Americans as a scourge who “invented” rape, stealing and basketball, and spoke of “the supreme White race.” It was labeled Kool Kids Klan — its three K’s underlined in a thinly veiled reference to the Ku Klux Klan.

The student who created the petition is white, as are two students who signed it, police said. Police called it “disturbing and reprehensible,” but determined that the petition, which was passed around during lunch on Jan. 6, did not rise to the level of a crime.

Anne Arundel school officials strongly denounced the petition last week, saying they were shocked and angered that such material would be produced, much less appear in a school, and that they would take “the strongest possible actions” against students involved.

Schools spokesman Bob Mosier said the students have been disciplined.

Gina Davenport, principal of Arundel High, in Gambrills, Md., said in a letter sent to parents last week that she was relieved that police resolved the Twitter threat quickly.

“Our school community has been shocked and saddened by the events of the last few days,” she wrote. “We are a diverse and united community that will persevere and withstand these tough times.”

She said that Arundel High “continues to be a safe and supportive environment that embraces all cultures” and asked parents to continue to talk to students about the events. “Those conversations are crucial to our ability to continue to move forward,” she said, adding that similar discussions would be happening in classrooms.