SIMI VALLEY, Calif. (AP) — Several environmental groups are suing state regulators over what they call the improper cleanup of radioactive waste at a former nuclear site near Los Angeles.

Consumer Watchdog and others filed a lawsuit in Sacramento Tuesday against the Department of Public Health and Department of Toxic Substances Control, which oversees the cleanup.

The groups argue that the state shipped low-level radioactive waste to landfills that were not licensed to take it. They want a temporary restraining order to stop the demolition of a plutonium fuel fabrication building.

State officials rejected the allegations, saying that the debris sent to facilities did not pose a threat to human health or environment.

Santa Susana was once home to nuclear research and rocket engine tests. In 1959, one of the reactors suffered a partial meltdown.