The US Embassy in Dublin has issued a security alert for "a potential for violence" at the Longitude Festival, which started yesterday in Marlay Park.
The statement read: "Local police are aware of the threat and will conduct comprehensive bag and person searches. The police have increased event security and are monitoring the situation."
However, the alert appears to have been issued without the knowledge of gardaí or festival organisers MCD.
A later statement by gardaí assured revellers it was safe to attend the festival.
"The festival is being policed appropriately following normal security risk assessment. A full and comprehensive policing plan is available on the Garda website, www.garda.ie, and on all Garda social media sites Facebook, Twitter and Instagram.
"No incidents have been reported to date," the statement continued.
Instructions issued by the US Embassy included "avoid Marlay Park and the areas surrounding the park", "keep a low profile" and "notify friends and family of your safety".
A spokesperson for the US Embassy said: "It is not uncommon for us to issue security alerts to US citizens when there are big events taking place."
Councillor for the Rathfarnham-Templeogue ward Carly Bailey said: "Gardaí will do what they can to make it safe - I'd trust them on that."