Gardaí said they made a number of drug seizures "within minutes" of the gates opening at the Electric Picnic festival in Co Laois.
There was early access to the festival site yesterday evening, ahead of music and events getting fully underway today.
In a Facebook post last night, gardaí in Laois-Offaly said they'd seized cocaine, ketamine, LSD and MDMA.
They moved to remind festival-goers that "any seizures made will have consequences for the individual".
The force has previously warned there'll be a "high-visibility police operation" in effect over the weekend.
They said: "Those who bring illegal drugs into the festival can expect to be caught and dealt with accordingly.
“Prohibited drugs are illegal and potentially life-threatening, especially when combined with alcohol, so we urge everyone to behave responsibly.
"We will be there to uphold the law and ensure the safety of all festival-goers."
This year marks the 16th Electric Picnic, with more than 57,000 people expected in Stradbally for the event.
