Freedom for Jack Russell trapped down West Coast tomo

Jacko the terrier was lost down a hole near Greymouth.

Jacko the Jack Russell has been freed after more than two days stuck down a West Coast tomo.

Three-year-old Jacko was possum hunting with his owner Shane Curtis, a professional pest controller, near Inangahua on Thursday morning when he chased a possum into the tomo.

Tomo are sinkholes formed when ground water dissolves underlying limestone rock.

Curtis' partner Willow Leigh said the dog had freed himself this morning.

"We have our boy!" she posted on Facebook. "He came out this morning somehow."

Leigh said the narrow tomo Jacko entered concealed a drop of at least five metres, and the dog had been trapped inside since just after 9am yesterday.

The couple had not stopped trying to rescue him since, starting with shovels and continuing with a hired digger.

Joined by Curtis' father and brother, they hadn't slept at all, Leigh said.

"He's our best friend ... he even cuddles up with my cat. He always goes hunting with my partner, he loves catching possums, he always comes home with a big smile on his face."

Both had taken time off work and Jacko's rescue had already cost them almost $1000 in digger fees.

But he was worth every cent, Leigh said.

"We don't care about money. We just care about getting this guy out alive ... we aren't gonna stop, no matter what, rain or whatever. We've been up all night and we are not stopping, the poor little dude."

They had tried to call police, fire and cave rescue teams for help.