Scientists from Canada and the United States are trying to save a starving and endangered orca. But they’ve hit a major roadblock in the process – finding her.

The four-year-old whale, dubbed J50, was last seen with her pod in open waters off Vancouver Island, B.C. on Saturday night.

Researchers believe the whale is starving, and possibly suffering from some kind of infection.

They’re concerned that without intervention, she may have only days to live.

“Her body condition is on par with past situation we've seen where a calf did disappear,” Lynn Barr of the National Oceanic and Atmosphere Association said during a conference call. “We are very concerned.”

Almost half a dozen vessels are out looking for the whales, with teams from the NOAA, the Vancouver Aquarium, the Department of Fisheries and Oceans, the Washington Department of Fish and Wildlife and others taking part in the search.

Scientists are hoping to get boats close enough for scientists to assess J50’s health, including taking a breath sample to test for infection, and inject her with antibiotics if necessary.

But the treatment won’t be possible if the whale is found in Canadian waters, according to Paul Cottrell of Fisheries and Oceans Canada, as officials are still dealing with paper work to ensure any efforts won’t harm the rest of the pod before the treatment is approved.

“This is a very dynamic situation,” Michael Milstein of NOAA told CTV Vancouver. “The veterinarians and biologists are constantly trying to consider what would have the best chance of success and kinda weigh those options while also being mindful of not disturbing the rest of the pod.”

Biologists have also considered feeding the orca salmon enhanced with vitamins or medication to try and boost her health, which would have to be undertaken 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."

It’s a unique intervention, but not unprecedented. Scientists have stepped in before to try and help preserve the orca population.

Back in 2002 scientists nursed an emaciated calf named Springer back to health in a sea pen before she was reunited with her pod off the coast of Vancouver.

But Milstein says that treating a whale in the wild like this has never really been attempted before. It’s a sign of how serious the situation has become.

“We know what’s going to happen if we don't intervene at this point,” said Michael Kundu, a whale advocate. “This population will be gone; I’m going to guess 30 to 35 years. So this is really our last chance.”

Losing J50 would be a serious blow for the southern resident killer whale population, which is made up of just 75 whales, as she is one of the few young females in the pod with the potential to reproduce.

Female orcas have had problems during pregnancy because of nutritional stress, and many of the calves who have been born in recent years have since died.

Just last week, a newborn calf, which was the first to be born in three years, died off the coast of Victoria, B.C.

Experts say that water quality, noise from marine traffic, which can affect the whale’s ability to hunt, and lack of Chinook salmon are the major causes leading to the decline in killer whale populations in the Pacific Northwest.

Even with intervention, there is no guarantee that J50 will survive, but scientists still plan to try – if they can find her in time.

With a report from CTV Vancouver’s Sheila Scott and files from the Canadian Press.