SEATTLE (AP) — The Latest on efforts to save a sick orca in Washington state (all times local):

5:05 p.m.

Efforts to find an ailing orca from a critically endangered population of killer whales off Washington state have come up empty, and a scientist who tracks them has declared her dead.

Ken Balcomb, of the Center for Whale Research, confirmed Thursday that he had declared the orca known as J50 dead after she failed to appear with her family in recent days.

Experts had been preparing last-ditch efforts to save the nearly 4-year-old, emaciated whale that included the possibility of capturing and treating her.

Her loss brings the population of orcas that spend much of their time in the Pacific Northwest to just 74. The whales have been struggling with a dearth of their preferred prey, salmon, as well as pollution and boat noise.

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1:03 p.m.

Teams are searching for an ailing, critically endangered orca that a scientist who tracks the whale population in the Pacific Northwest says is likely dead.

Experts have been preparing last-ditch efforts to save the nearly 4-year-old, emaciated whale that included the possibility of capturing and treating her.

Ken Balcomb of the Center for Whale Research said Thursday he believes the whale known as J50 "is gone."

Michael Milstein, a spokesman for NOAA Fisheries, said boats and planes in the U.S. and Canada are looking but that Balcomb usually makes such calls on missing whales because he keeps the population data.

He said J50 has not been seen in recent days with her family. J50 went missing earlier this month but later turned up.

The loss of J50 would bring the number of southern resident killer whales to just 74 animals.