Editor's note: For a full investigation into the Anoka-Hennepin student suicides, watch "CNN Presents" on Sunday, July 24, at 8 p.m. ET.
(CNN) -- Two advocacy organizations filed a federal lawsuit Thursday against Minnesota's largest school district, challenging what they call "pervasive anti-gay harassment" in its schools, the groups said in a news release.
The Southern Poverty Law Center and the National Center for Lesbian Rights filed the lawsuit on behalf of "five students who have faced severe anti-LGBT (lesbian gay bisexual transgender) bullying and harassment while attending school in the (Anoka-Hennepin) district," a joint news release states.
The school district issued a news release stating it's reviewing the complaint, noting it "takes strong exception to the outrageous media statement the district is not concerned about the safety of its students."
The filing comes amid a federal investigation into "incidents involving harassment and bullying" in the school district, located in north suburban Minneapolis, according to a Department of Justice e-mail to CNN.
The Justice Department and the Department of Education's Office of Civil Rights are looking into a complaint regarding "allegations of harassment and discrimination in the Anoka-Hennepin School District based on sex, including peer-on-peer harassment based on not conforming to gender stereotypes," according to a district memo provided to CNN.
The party filing the complaint to the federal agencies was not named due to privacy concerns.
The federal investigation follows a string of seven student suicides in less than two years, which stirred public debate over the district's sexual orientation curriculum policy.
Parents and friends say four of those students were either gay, perceived to be gay or questioning their sexuality, and they say that at least two of them were bullied over their sexuality.
The school district denies any connection between the bullying and the suicides.
It's unclear whether the suicides or the policy are a significant part of the federal investigation.
The controversial sexual orientation curriculum policy, adopted in 2009, states that staff must "remain neutral on matters regarding sexual orientation" and that "such matters are best addressed within individual family homes, churches or community organizations."
The policy is local to the Anoka-Hennepin district rather than statewide. However, at least eight states -- Alabama, Arizona, Louisiana, Mississippi, Oklahoma, South Carolina, Texas and Utah -- have statutes specifying varying limits on classroom instruction regarding homosexuality. Tennessee considered similar legislation this year.
Community supporters of the so-called neutrality policy say it is constitutional and consistent with the Minnesota Human Rights Act, which protects rights based on sexual orientation but states that nothing in the law shall be construed to "authorize or permit the promotion of homosexuality or bisexuality in education institutions."
Gay rights advocates who oppose Anoka-Hennepin's neutrality policy say the school district has misinterpreted the intention of the state's human rights law.