Two men and two women were beaten with crowbars during the attack by a six member gang.
The incident occurred in the Townley Hall area between Slane and Drogheda at around 4.30am this morning.
The two couples had been in a car when they were attacked by a gang and beaten up.
One of the women was dragged into the forest where she was raped.
Three teenagers and a juvenile were arrested at Our Lady of Lourdes Hospital, Drogheda, after one of them presented for treatment to injuries.
Three of them are being questioned in Drogheda Garda Station, while another is being detained in Dundalk.
A fifth person was arrested this afternoon. He is being questioned in Dundalk Garda station.
The scene of the attack was sealed off all day and the victims' car was removed for forensic examination.
All four victims of the attack are receiving medical treatment.
