Gardai in Galway have been asked to investigate the gas oil leak which caused pollution in Galway Bay earlier this week.
However, it is understood that there is no early evidence of criminal activity at the Statoil terminal, where the incident took place.
Statoil has confirmed that an estimated 50,000 litres of gas oil, or home-heating oil, leaked from a storage tank, some of which ended up in the bay.
Clean-up efforts are expected to continue in the harbour area for several days.
It has now emerged that the leak took place some hours before the alarm was raised. Statoil confirmed yesterday that an alarm system was triggered at 10 p.m. on Tuesday, but there was no sign of any problem. The area was checked repeatedly until 3.30 a.m. on Wednesday.
When the terminal manager arrived at 7.45 a.m. on Wednesday, there was evidence of a serious leak, and emergency systems were put in place at 8.30 a.m.
Galway Harbour Company activated its oil pollution emergency plan, as did the company, but the harbour authorities provided most of the anti-pollution equipment.
Statoil is investigating the incident, and believes it can be traced to a valve installed on the storage tank as part of safety drenching systems.
It is understood that the water valve was left on, filling the tank and forcing oil up to the surface.
However, the bunding system (moat-type structure) installed as part of safety procedures failed to contain the spill, and Statoil is considering taking legal advice on this.
The storage tank was three years old, and the bunk was of high specification.
Engineering consultants have examined it, and checks are also being carried out throughout the terminal, a company spokeswoman said yesterday.