The New Jersey Division on Civil Rights and the New Jersey State Interscholastic Association on Monday urged school officials "to redouble efforts to keep bias out of interscholastic sports."

In a joint letter to school principals statewide, Craig T. Sashihara, who heads the Civil Rights Division in the state Attorney General's Office, and Larry White, executive director of the NJSIAA, pledged to work together to combat bias in school sports, and asked school districts for their help following several racial incidents involving high school athletes.

"Particularly in light of recent events, it is important that you join us in sending a message to the public, to student-athletes, and to parents, coaches, and all other stakeholders that we are united in our commitment," the joint letter said.

The letter didn't cite any specific cases or refer to a May 1 incident at Haddonfield Memorial High School that made national headlines. School officials said a lacrosse player used a racial slur against a black female athlete from another school, conduct the interim superintendent later denounced as unacceptable.

When no one would admit to making the slur or identify the player who did, the superintendent canceled the lacrosse season, ending a promising run for a team widely viewed as a contender for a state championship.

Haddonfield School Superintendent Larry Mussoline, who took his post after the incident, welcomed the statement Monday.  After several meetings with parents and the lacrosse team, the district has completed its investigation, he said.

"Incidents of racial bias have been all too commonplace in America's great institutions of late," he said in an email. "It's probably overdue for statements like this one coming from state leaders."

The incident remains under review by the state Attorney General's Office.

In the letter to the principals, state officials sought to reinforce a 2013 memorandum of understanding between the civil rights division and the athletic association on a policy designed to crack down on harassing conduct related to race, gender, ethnicity, disability, sexual orientation, or religion. The letter asked school officials to review the guidelines  — among the first of their kind in the country —  and ensure that coaches, staff and students uphold "these principles of fairness, decency and sportsmanship."

"High school sports instill valuable life lessons," the letter said.

>>READ MORE: 'I was in shock': Teen witness of racial incident that ended Haddonfield boys' lacrosse season

In a statement, Lloyd D. Henderson, president of the Camden County East Branch of the NAACP, blasted Monday's statement.

"Appears to be passing the buck to me," Henderson said. "Clearly schools, leagues, conferences, officials did whatever they wanted to do, whenever they wanted to do it. Where and when was the training since 2013?"

The civil rights group last month conducted diversity training in Haddonfield and has said additional sessions will be held.

In a June 7 letter from White, the NJSIAA accepted the corrective action plan submitted by Haddonfield High principal Charles Klaus to address the racial incident, and also considered the matter closed. White, in a letter to Klaus released to the Inquirer and Daily News, said the athletic association accepted Haddonfield's corrective plan and believes it will  "provide for sustainable changes that hopefully shall foster a culture of acceptance and inclusion."

Under the plan, the district plans to work with the Anti-Defamation League on several programs, become a "No Place For Hate" school, select 25 students and two staff members to undergo training by the ADL and work with area schools with more diverse student populations. All sports teams will get training on "diversity, acceptance and belonging" and coaches and athletes will be required to sign off on a NJSIAA statement on sportsmanship, the plan says.

White applauded the district, noting that "although this very difficult situation occurred, the Haddonfield School District administration responded very quickly and decisively, made very difficult decisions based on the fact that no boys' lacrosse team member admitted guilt."

White said the matter is closed. The athletic association has authority to investigate possible violations of its sportsmanship rule and impose disciplinary action such as disqualifying an athlete or team from competing because of a verbal, written or physical conduct related to race, religion, ethnicity, gender, disability, or sexual orientation.

Neither White nor Klaus was available for additional comment.

A complaint filed by Sterling with the athletic association stemming from the Haddonfield incident that was referred to the state Attorney General's Office as a possible bias incident remains under review by the civil rights division, said Lee Moore, a spokesman.

The female athlete, from Sterling High School, was on the track stretching when from five to seven white Haddonfield lacrosse players walked by her, and one told her to "Move, 'N-word,' " according to a police report. The slur was heard by at least three athletes from other schools. Haddonfield 's internal investigation said statements from witnesses from Haddon Heights corroborated her account.

Then-interim  Superintendent David Lindenmuth announced on May 11 that he had suspended the team's season after the investigation could not identify the student who used the slur. The Sterling student said she could not identify the person because the lacrosse players were wearing helmets.

It is believed to be the first time that a school in New Jersey has canceled a sports season in progress since 2014, when the Sayreville football program was shut down by incidents of bullying, harassment, and intimidation, according to the athletic association.

Some supporters of the lacrosse team have suggested that the Sterling athlete may have misheard or misunderstood a remark and that Lindenmuth unfairly punished the entire team. Haddonfield withdrew from the NJSIAA tournament where it was expected to compete as the No. 7 seed in South Jersey Group 1.

Sterling, in its complaint, cited another incident earlier in the school year that allegedly after a girls' basketball game with Haddonfield on Dec. 19. A white Haddonfield assistant coach gave high-fives to the opposing team's white players, who were lined up to congratulate the other team, but skipped two black players, the complaint says.

The population at Haddonfield Memorial High School, which enrolls about 850 students in grades 9-12, is 90 percent white, 4.2 percent Asian, 2.2 percent Hispanic, 1.5 percent black, and 1.9 percent multiracial.