Three men who were arrested on Thursday morning near Ballybofey have all been released without charge.
They were arrested after a bomb was planted under a police officer's car in Derry.
At around 4am on Thursday morning the three men were arrested in Killygordon after their car was stopped and searched.
The car was examined and searches were carried out in the area where the car was stopped.
They were held on suspicion of terrorism offences.
The bomb was discovered in Glenrandel in Eglington village after suspicious activity was reported to police at around 2.45 on Thursday morning.
The three men are understood to be aged in their late 20s and late 30s.
Two of the men were held in Letterkenny Garda Station, while another man was held in Milford Garda Station.
They were released without charge yesterday evening.
A file is being prepared for the Director of Public Prosecutions.