The woman works in the medical wing of Cloverhill prison in Clondalkin.

She had a minor disagreement with a 49-year-old prisoner who was a close friend of 'The General', Martin Cahill.

The prisoner, who is serving a short sentence, threatened the woman with physical violence to a degree where she felt that her safety was at risk. She officially reported the incident to prison management and the inmate was disciplined internally. He reacted furiously to this and told the woman that she would be "got" when she left work.

Just days later, the staff member, who lives in Dublin, woke up to find that the two cars in her driveway were on fire. One car belonged to the prison officer and the other was owned by her husband.

Gardai and the fire service were called to the scene and an investigation concluded both vehicles were set on fire maliciously.

The woman is married with young children and both gardai and the prison service are concerned for her safety. She is said to be extremely traumatised by the incident.

The prisoner has been interviewed but has denied any involvement. Detectives are attempting to get records of any phone calls he made in the days before the incident, which occurred on 4 September.

The prime suspect has over 100 convictions for a wide range of offences such as robbery, motor offences and public order incidents.