PORTLAND, Ore. -- NOAA's Fisheries Service said that the cause of death of six sea lions found on two traps at Bonneville Dam Sunday remains unknown, they were not gunshot wounds as originally reported.

The necropsies did identify numerous shallow puncture wounds in one animal that are consistent with sea lion bite marks, according to NOAA. An investigation is ongoing by the agency to determine how the animals officially died.

The carcasses of two California sea lions and one Steller sea lion were each contained in two closed traps, said Rick Hargrave, a spokesman for the Oregon Department of Fish and Wildlife.

NOAA is investigating how the doors to the traps could have been closed because in the trapping operations, the traps are left open so the sea lions get used to them. When wildlife agents are ready to remove the sea lions, they close the traps.

Seven California sea lions were trapped on the Columbia starting April 24 after the 9th U.S. Circuit Court of Appeals approved their capture. One died during a medical inspection before transfer to a Sea World park.

Anyone with information that may assist in this investigation is asked to call the NOAA Enforcement Hotline at 1-800-853-1964.