MEXICO CITY (AP) — Rescuers in Mexico were partially able to free a humpback whale that became entangled in a fishing net illegally set inside a refuge for the critically endangered vaquita porpoise in the upper Gulf of California, a conservationist group said Monday.

In a statement, the Sea Shepherd group said it was alerted on Friday to the trapped whale which was struggling from the net, several hundred yards (meters) long and “tightly wrapped” around its head, body and tail.

“Alive but exhausted, the animal had suffered numerous injuries to its pectoral fin and tail and was unable to dive under the strain of the gillnet,” Sea Shepherd said.

Rescuers worked for several hours to cut the netting from the whale. By early evening its head and body were free and it disappeared into the deep.

But Sea Shepherd warned that some remnants of the netting remained wrapped around its tail, a possible long-term threat.

The rescue took place in what’s known as the refuge’s “critical zone,” where several vaquitas have been spotted. It’s the same area where a Sea Shepherd vessel came under gunfire earlier this month by men in small boats.

Only about a dozen or so of the porpoises are believed to remain in the Gulf of California, their only natural habitat.

They are critically threatened by illegal gillnet fishing for totoaba, a species whose swim bladders can sell for thousands of dollars in China.

As the recent rescue shows, it’s not just the vaquita that’s threatened by illegal net fishing in the refuge.

Sea Shepherd said it rescued an entangled humpback there in 2016, and the following year it discovered a dead Bryde’s whale also caught in a gillnet.

“This whale entanglement is another example of why it is so important to continue to protect the Vaquita Refuge against illegal fishing,” Sea Shepherd captain Octavio Carranza said in the statement. “It is also a sad reminder of what the vaquita deals with on a daily basis in its quest for survival.”