An international effort to save an ailing orca from the endangered southern resident killer whale population has hit another roadblock. 

Time is ticking for J50, but the four-year-old female’s pod hasn't been seen since Saturday night, despite the work of U.S. and Canadian scientists who are scouring the waters off Vancouver Island and Puget Sound on about half a dozen vessels.

"We have not seen them," said Michael Milstein of the National Oceanic and Atmospheric Administration. "There's been some challenges with fog but the crews have been out looking and (they're) ready and waiting."

Past sightings suggest the killer whale is starving and lethargic, and researchers believe she's suffering from some kind of infection. There are concerns she might only have days left to live, and her death would be a major blow to the population of just 75 orcas.

Meanwhile, as various teams from the NOAA, the Vancouver Aquarium, the Department of Fisheries and Oceans, the Washington Department of Fish and Wildlife and others search for J50's pod, veterinarians and biologists are weighing potential treatment options.

Milstein said they're currently considering a plan to get close enough to the killer whale that they can take a breath sample that will help assess her state, then use a syringe on a pole to inject the orca with antibiotics.

The NOAA said that method would be preferable to feeding J50 medication-stuffed salmon, which would have to be administered on a daily basis.

"As you can tell we've had a lot of challenges in seeing them daily," Milstein said. "The benefit of doing (an injection) is we can deliver a longer lasting dose of antibiotics."

Milstein said he doesn't believe the strategy has ever been attempted on a wild orca before, and there's no guarantee it would work.

"The biologists that are out there … are quite experienced at working around the whales," he said. "There are ways to maneuver in such a way that it doesn't present any safety risk to the crew or to the whales. But it's always an uncertain venture when you're attempting something out in the wild with a wild animal."

J50’s health is so important because she’s one of the few whales in her pod with the potential to reproduce. The same pod also includes J35, the whale recently captured in heartbreaking photographs pushing the body of her deceased calf to the surface.

While J50’s situation is unique, it’s the not the first time humans have intervened with wild orcas on the west coast.

In 2002, an emaciated orca calf named Springer that had become separated from her pod was nursed back to health in a seapen near Hanson Island. She was successfully reunited with her pod in B.C. later that year.

Michael Kundu worked on Springer’s rescue effort, and is supportive of the efforts to save J50.

“There’s two reasons why I think we should try,” Kundu said. “One, is to get good at the science. And two, even though this might not help this whale survive. We’ve got to do something. There’s no reason for us to simply let this go without learning from the process. We’re obligated to do it.”

Even if experts are able to medicate J50, finding her again may be a problem.

While researchers are aware of some of the pod’s patterns, there is no satellite tracking program in use in the area.

Canadian researchers have never used trackers on orcas, but researchers in the U.S. have.

An 2016 an orca dubbed L95 that had been embedded with a tracker by American researchers was found dead on a Vancouver Island beach, raising concerns about the use of satellite tags. The satellite tracking program is no longer in use.

Experts are hopeful J-Pod’s struggles will bring attention to the dwindling numbers of southern resident killer whales. 

A task force put together in March by the governor of Washington State to address the struggles of orcas has a scheduled meeting Tuesday to discuss what additional steps can be taken to protect the fragile population.