The elderly woman had been suffering from poor health for some time and died last night while the search is on going for her son.
Diarmuid Twomey has been missing since Sunday, December 20th.
The Cork man was last seen by his partner when they hailed a taxi at three in the morning.
Feeling ill, he had not taken the taxi and Mr Twomey’s phone was found in a farmyard at Ballinahina at 11:30am on the morning of December 20th.
Gardai have sinced appealed for three men to come forward, stating they may have a connection to the search.
The men in question were seen visitng Whitechurch Recycling Centre between 6am and 6:30am the same morning that Mr Twomey went missing.
Diarmuid Twomey was wearing a blue check shirt with beige chinos and brown runners. He is of stocky build and is 6ft in height.
Gardai are appealing for anyone with information to please get in contact at Gurranabraher Garda station on 021 4946200.