Rescuers have restarted a robot at the Pike River Coal mine and it has now travelled 1km.
The robot stalled on Tuesday morning about 500 metres into the mine tunnel. It has moved another 500 metres.
There is no explanation as yet for the halt, but unconfirmed media reports say its battery went flat.
A second Defence Force robot is also in the tunnel and moving up the roadway.
The Defence Force says the robot operates with four cameras in its standard configuration.
A third, more advanced robot, which can go into an explosive atmosphere, arrived at Hokitika on Wednesday morning from the Royal Australian Air Force in Perth.
Another robot is to come from the United States.