SUDBURY, Ontario (AP) — The last four miners trapped deep below the surface in the Totten Mine climbed to safety early Wednesday morning, the company that owns the mine near Sudbury, Ontario, said.

Vale said the operation that saw 39 workers climb a series of ladders with the aid of rescue crews is complete.

“This is tremendous news flowing from very difficult circumstances,” Vale CEO Eduardo Bartolomeo said in a statement.

The last miner reached the surface shortly before 5 a.m., said company spokesman Jeff Lewis.

The workers became trapped on Sunday when a scoop bucket being sent underground detached and blocked the mine shaft.

Some of the miners were trapped as deep as 1,200 meters (nearly 4,000 feet) below the surface, the company said.

Bartolomeo, who was on site, said Vale will investigate what happened “so that the company can learn from it and take steps to ensure it never happens again.”

Vale said the workers stayed in underground “refuge stations” and had access to food, water and medicine before climbing out.

The province’s Ministry of Labor, Training and Skills Development said an inspection team will investigate the incident.

The Totten Mine opened in 2014 and produces copper, nickel and precious metals. It employs about 200 people.