Gardai stopped a vehicle in south Inishowen yesterday after it had been observed being driven in an erratic manner.
The driver was then arrested on suspicion of drug driving after they failed a roadside drug test.
The driver had tested positive for Cocaine and Benzodiazepines.
Gardai say that a further investigation will follow.
Meanwhile, Gardaí in Carndonagh conducted patrols of beauty spots yesterday to ensure that vehicles were parked in a legal manner and that emergency access was not being blocked in any way.
They also spoke to drivers in relation to car security and advised them to ensure that their car was locked when unattended and to refrain from leaving valuables in them.
