Peabody Energy (BTU) said Monday it may walk away from its planned acquisition of Anglo American's steelmaking coal assets if problems at the Moranbah North Mine in Australia are not resolved within the timeframe outlined in their agreement.

The mine has been shut since a gas ignition incident in March, the company said.

"A substantial share of the acquisition value was associated with Moranbah North, yet there is no known timetable for resuming longwall production," said Peabody Chief Executive Officer Jim Grech.

Shares were 8.5% higher in recent premarket activity.