LOS ANGELES (AP) _ A civil rights group sued the Los Angeles school district Wednesday, demanding that officials reverse their decision to walk away from the $170 million, half-built high school that sits on a toxic site near downtown.

The lawsuit was filed in Superior Court on behalf of a coalition of parents, teachers and students by the Mexican American Legal Defense and Educational Fund, a nonprofit advocacy group.

The Board of Education voted in January to jettison the Belmont Learning Center, the nation's costliest high school, after environmental tests at the site, a former oil field, revealed dangerously high levels of sulfur dioxide and potentially explosive methane gas.

The state-of-the-art learning center originally envisioned was a long-promised replacement for aging Belmont High School, which serves a largely poor, minority neighborhood that is so crowded with students that thousands are bused to other campuses each school day.

The lawsuit accuses the district of violating state law by failing to commission a new environmental impact report after dropping plans to finish the school. The lawsuit asks that the district be ordered to prepare a new report.

School officials said in a statement they are drafting a plan to commission a new report and have not ruled out any future plans for the site, including using it as a school.