The Police Ombudsman for Northern Ireland (PONI) is to publish a report later on the IRA firebomb attack on the La Mon Hotel, outside Belfast, which killed 12 people.
The attack on 17 February 1978 at the County Down venue is considered one of the most horrific attacks of the Troubles.
A bomb, placed outside a window, was attached to cans of petrol mixed with sugar, sending a huge fireball into the hotel, where 400 people were attending a dance.
The watchdog's report is likely to be critical of aspects of the original investigation.