A gray whale with a metal frame caught around its head is making its way up the coast of California. No one knows exactly where the whale is or how it got entangled, but a bunch of volunteers are currently keeping their binoculars trained on the ocean to catch it. They hope to find the whale so professionals can free it before it dies or disappears.

The animal was first spotted between San Diego and Los Angeles on Saturday April 1st, and it is expected to make an appearance near San Francisco between Friday and Saturday, according to calculations by Peggy Stap, executive director of the nonprofit Monterey Bay Marine Life Studies. She is also co-founder of the Whale Entanglement Team — a volunteer group of spotters and certified disentanglers that works with the National Oceanic and Atmospheric Administration to respond to reports of entangled whales.

(Whale watchers who see an entangled whale should call NOAA’s hotline at (877) SOS-WHALE and should not attempt to help the whale themselves.)

Entanglements are not uncommon for whales and other marine mammals, which can become stuck on traps and abandoned fishing gear. When that happens, they can drown, starve, or die from infection. The gray whale with the metal frame is the second one entangled in fishing gear to be spied along California’s coastline in less than a month. In March, a gray whale with gill nets and fishing lines wrapped around its tail was spotted several times off the coast of Southern California — but conditions were too dangerous to attempt a rescue, GrindTV reports.

ENTANGLED GRAY WHALE ALERT: update! We resighted this entangled gray whale off our Gray Whale Census at Point Vicente... Posted by American Cetacean Society - Los Angeles Chapter (ACS/LA) on Tuesday, March 21, 2017

Right now, Eastern North Pacific gray whales are making their long migration from the shallow lagoons of Baja, California, and Mexico, where they breed, to the Bering and Chukchi Seas off the coasts of Alaska, where they feed. These massive creatures, which can grow to 50 feet in length and up to 80,000 pounds, are bottom feeders — sucking up the sediment on the ocean floor and the little crustaceans that live in it.

It’s not at all clear how the gray whale that’s been making headlines got entangled in the metal frame. We don’t even know what the frame might be. “We’ve dealt with lots of weird things, and more often or not the entanglements involve rope,” says Pieter Folkens, a marine mammal illustrator who has been specially trained by the National Oceanic and Atmospheric Administration to free whales from entrapping lines and fishing gear. “We’ve never had a whale wrapped in metal before.”

It’s possible that it’s a piece of metal from an aquaculture pen, Folkens says, but that’s a “W-A-G — wild ass guess,” he adds. In fact, we don’t even know if the frame goes into the whale’s mouth or around its chin at the moment, which complicates attempts to plan a rescue.

Grid View Pieter Folkens worked to free this whale that had become entangled on spot prawn traps. Image courtesy of Pieter Folkens, acquired under NOAA MMHSRP Permit #18786

A whale rescue in 2015. Image courtesy of Pieter Folkens, acquired under NOAA MMHSRP Permit #18786

Whales entangled in rope like this one are more common, Folkens said. The one making headlines with its head caught in a metal frame is unusual. Image courtesy of Pieter Folkens, acquired under NOAA MMHSRP Permit #18786

This whale has a cord caught around its head. Image by D. Croft, courtesy of Pieter Folkens and acquired under NOAA MMHSRP Permit #18786

The reports of entangled whales are on the rise — with 71 entangled whales reported off the West Coast from Mexico all the way to Canada in 2016. Of those, 48 were confirmed — a record number since NOAA began keeping count in 1982. That could be due to a variety of reasons, including a rebounding population of whales, and even just more people reporting the entangled animals to authorities.

The Dungeness crab fishing season also opened later than usual last year, because of unsafe levels of the neurotoxin domoic acid. With the shortened season and limited areas open to fishing, the crab traps were more concentrated in places that also had a lot of humpback whale activity. “So there was a pretty heavy co-occurrence, or overlap, between high concentration of whales, and high concentrations of gear,” Justin Viezbicke, the California stranding coordinator for NOAA, told The Verge. “That usually equals problems.”

In 2016, the California Dungeness Crab Fishing Gear Working Group came up with a new best practices guide to try and curb the number of entanglements. “We very much are trying to work with the fishermen, and we realize that these guys’ livelihoods depend on it,” Viezbicke says. But, he adds, these entanglements could put a sizable dent in the populations of whales living off the West Coast of North America. “If we keep going at this rate, it’s problematic — and so we have to find more solutions, and try to be more preventative.”

Folkens is currently waiting for the whale to be spotted again. If it is, and if conditions are safe enough to send a team into the water, the first step will probably be to affix a satellite tracking buoy to whatever is entangling the whale, Stap says. That way, they’ll be able to find the whale again. “You’ve got to think about it like a moving needle in a moving haystack,” she says. The team may also trail floating balls off the whale to slow it down, making it easier for a disentangling team to catch up to it again.

But Stap, Folkens, and Viezbicke say they won’t know what they’ll be able to do to free the whale until they have more information. “Do we add more drag to something that’s on the head? If it’s in a bad position it could cause more problems than good,” Viezbicke says. “That’s the hard part for us — that there’s still a lots of unknowns. And with unknowns, there’s increased risk.”