Moranbah North is the sister mine of Anglo American's Grosvenor mine, which was the site of a methane ignition incident last month that injured five mine workers.
A Queensland Mines Inspectorate spokeswoman said it was notified of a planned withdrawal of workers at Moranbah North mine following a loss of electrical power at the mine site.
"QMI is on site investigating this high potential incident," she said.
"No injuries were reported to the QMI in relation to this incident."
An Anglo American spokeswoman said Moranbah North mine was repowered only when gas levels were within acceptable limits.
Construction, Forestry, Mining and Energy Union district president Stephen Smyth told ABC the mine was re-energised without a thorough check.
"[When] you repower that mine or re-energise that mine, you're sending electric power back into the mine through cables and if there's gas present, then you've got a big issue," Smyth reportedly said.
"You cannot play it down, the seriousness of what's happened.
"You can end up with explosive mixes of gas.
"I've been made aware that they did have high gas levels in certain areas of the mine at this time from the ventilation being reduced."