A demonstration in support of those on board the Gaza aid flotilla, which blocked the southbound lane of the Dublin Port Tunnel, has ended.
Transport Infrastructure Ireland said the incident has been cleared and the Port Tunnel said traffic metering is in place.
At least 14 Irish citizens are being held after the Global Sumud Flotilla was intercepted by Israel.
Gardaí said the southbound lane in the Dublin Port area is closed, along with several other road closures in the area.
The Irish Road Haulage Association (IRHA) said hundreds of freight trucks were affected by the ongoing traffic delays.
Eugene Drennan said some members had been queueing and stuck in traffic since 2.30pm this afternoon.
He said the 4.30pm Stena Line ferry left without its full complement of trucks on board as many vehicles could not get through the gridlock.
The next sailing with Irish Ferries is at 7.45pm and many trucks are expected to miss that too.
He said people are entitled to protest but "our biggest supply chain from Dublin to Holyhead is being disrupted."
"Accompanied with the coming storm, this puts us in a very precarious position," Mr Drennan added.
He said the IHRA had raised this issue at committees before as to how easily this could happen, and who would have responsibility, whether it was the gardaí or the Port Authority.
Stena Line said was aware of the ongoing traffic congestion.
It said while it tries to accommodate drivers where possible, it is required to maintain its schedule on the Dublin to Holyhead route due to berth-sharing arrangements.
Its sailings have therefore not been delayed.
Former president of Trinity College Dublin Students' Union Jenny Maguire, who took part in the demonstration, said the protest is blocking traffic on both sides.
She added that protesters spoke to drivers about why they took the action.
"We are here today because we are human. The rules meant to stop this genocide are not working," Ms Maguire said.
The demonstration started outside Leinster House earlier this afternoon.
A few hundred people, many with Palestinian flags gathered at the junction of Molesworth Street and Kildare Street.
The demonstration was addressed by activists and a number of Opposition politicians.
Additional reporting Joe Mag Raollaigh
