The UK government says the field, which is opposed by environmental campaigners, could be producing gas by the end of this month.
In total 116 children and 28 adults were killed when a colliery spoil tip collapsed on 21 October 1966.
While not naming the disgraced former MP, the Metropolitan Police has issued a statement confirming a 63-year-old man is being investigated.
The prime minister provided little detail, and there are questions over shifting the fees onto unit costs.
The school went into lockdown and parents gathered at the gates as they waited for news about their children.
It is understood Eleanor Barnfield, from Bridgend, had been stabbed before the crash.