SANTA FE, N.M. (AP) — The state Supreme Court has ruled a uranium company's insurance policies may cover costs of cleaning up contamination at a former mine in northwestern New Mexico.

The ruling on Thursday sends the dispute back to a district court to determine what insurers must pay for, if any, involving a cleanup by United Nuclear Corp. at the Northeast Church Rock mine near Gallup. The site is adjacent to the Navajo Nation.

The court decision hinged on an insurance provision excluding coverage for pollution damages unless the discharges were "sudden and accidental." The court concluded the term "sudden" meant unexpected rather than happening over a short period of time. An insurance company had contended its policies provided no liability coverage because environmental damage at the mine happened over many years.