Five people were arrested during clashes between Shell to Sea protesters and gardaí at the Corrib gas terminal site in Co Mayo yesterday.
A protester was arrested as a result of an alleged assault on a garda who was taken to hospital with a suspected broken nose.
The protester was released without charge and a file was sent to the Director of Public Prosecutions.
Four others were arrested for public order offences, but were also released without charge.
Over 150 gardaí, including members of the riot squad public-order unit, policed the crowd of about 200 people who had gathered from Dublin, Belfast, Cork, Donegal and the local area for "a sit-down protest" which began at 7am yesterday.
Among those taking part were two of the Rossport Five, Willie Corduff and Vincent McGrath.
Clashes broke out when about 50 protesters scaled the refinery's main gate and then allowed other protesters to file through at about 8.30am. Protesters said they held the gates open because of the crush outside, but gardaí said their behaviour was unacceptable.
Supt Joe Gannon said: "The protesters seem to regard themselves as having some role in the policing function and I'm not going to tolerate anarchy on the roads of north Mayo or anywhere else."
Organiser Caoimhe Kerins of Dublin Shell to Sea said gardaí had kicked protesters while they were on the ground inside the terminal.
She said that the pipeline still had to get an integrated pollution prevention control licence from the Environmental Protection Agency.
"The perception that this project is done and dusted is completely wrong," she added.
"People have appealed to the Government time and time again, and to local politicians, but to no avail.
"They [the protesters] feel they are just hitting a blank wall and feel they have been left with no choice at this stage."
Ray Hanrahan from Cork Shell to Sea said: "I'm here today to show support for a community under siege.
"This is about our natural resources and nobody voted for our resources to be given away. We are being impoverished by an unholy alliance between a multinational and a delinquent Government."
Gardaí had been drafted in for the operation from Galway, Sligo, Limerick, Cavan and Monaghan.
Chief Supt Tony McNamara said that they had been prepared for trouble. "We always have to have a plan B. If the protest had remained peaceful, however, we wouldn't have deployed all the gardaí," he said.
Shell Ireland said the trouble was caused by people with "no link" to the region.
Spokesman Colin Joyce said the protest was supposed to have been peaceful but turned out to be "highly irresponsible".
"It shows once again Shell to Sea appears unable to control its supporters who are not from the local area," Mr Joyce said.
Shell said the protests did not stop the 300 workers at the site from going about their work and disruption had been kept to a "minimum".
Shell also said the foundations for the terminal had been already laid and it would be fully up and running within two years.