Marine scientists are raising the alarm over the number of grey whales washing up dead on West Coast shores recently.

So far this migratory season, as the whales make their way from Mexico to Alaska, 70 dead whales have been found.

Many are skinny and malnourished. Scientists with the U.S. National Oceanic and Atmospheric Administration (NOAA) say the number is only a fraction of the number that are actually dying off.

The migratory season for B.C., Washington state and Alaska is only halfway over and 30 whale have already washed ashore in these regions. The yearly average for the West Coast of the United States is 14.8 dead grey whales, while B.C. typically has two.

The die-off is great enough for the NOAA to declare an Unusual Mortality Event (UME) on Friday, which will trigger a scientific investigation into the cause. 

It's the first time a UME has been declared since 2000, when 100 grey whales were found dead onshore and an estimated 6,000 died in total.

Scientists from up and down the coast will now work together to figure out what is causing the deaths. 

They hope to perform as many necropsies on grey whales as they can to determine if disease, environmental changes or something else is causing the deaths.

Paul Cottrell, a marine mammal coordinator with Fisheries and Oceans Canada, says the news is not all bad.

"The good news is that we're seeing this grey whale population is estimated at 27,000, so it's a healthy population and this population might be nearing where this population is sustainable," Cottrell said.

Grey whales in the Pacific Ocean typically give birth to 1,000 calves per year. They also have a flexible diet allowing them to find many different food sources.

Anyone who spots a stranded or distressed whale is asked to call Fisheries and Oceans Canada immediately.