The department was shut to the public for three hours on Tuesday night - with three patients being diverted to the Altnagelvin Hospital in Londonderry - while fire crews and staff battled to prevent damage to the hospital.Services resumed in A&E at 11pm. Clinical areas were not affected by the flooding.Seán Murphy, General Manager, Letterkenny General Hospital, stated: "I want to acknowledge the hospital staff, the ambulance service, the staff at Sligo Regional and Altagelvin Hospitals, our local GPs, the fire service, the council and the Gardaí for their cooperation."We regret any inconvenience caused to patients and their families."The emergency services remain at the scene in anticipation of more heavy rainfall, which is expected on Wednesday. An investigation into the cause of the flood has already started.Last year, a huge deluge hit the brand new hospital causing €43m worth of damage.Mr Murphy continued: "Although services are now back to normal, we would like to remind the public to keep the Emergency Department for emergencies and to contact their GP or GP Out of Hours services in the first instance.""We would also like to remind people that visiting the Short Stay Ward in the hospital has been suspended for the time being due to cases of norovirus on the ward."If relatives are concerned about patients on this ward, a nominated person from each family can liaise with the Clinical Nurse Manager on the ward regarding planned visiting. The contact number is 074 912 5888, extension 4084."People who have vomiting and diarrhoea symptoms should not attend the hospital but should contact their GP in the first instance if they have serious concerns."We would like to thank patients and the public for their cooperation."Sinn Féin councillor Gerry McMonagle said he was angry to yet again see the hospital close its emergency department because of flooding.He said: "It is one unmitigated disaster, not just for the hospital but for the people of Donegal."Once again our new accident and emergency has been ruled out due to 15-20 minutes max of rain, this is just not good enough."Parts of NI also experienced flooding due to torrential rain overnight, with Moneymore and Magherafelt in Co Londonderry and Omagh, Co Tyrone among the areas worst affected.The Northern Ireland Fire and Rescue Service dealt with 33 call outs between 6pm and midnight, and dealt with 11 incidents.One woman, who was concerned for her safety, was assisted out of her house, although her property was not flooded.Due to storm-damage to Magherafelt Courthouse, all business listed for Wednesday will be carried out at Antrim courthouse.A statement from NI Courts and Tribunal Service said that an inspection will be carried out to assess the damage.The Met Office has said heavy and thundery showers can be expected through into Wednesday morning, bringing a risk of localised flooding.