Police are reviewing evidence to determine whether charges will be laid against any of the protesters who crossed the Auckland Harbour Bridge on Sunday.

Waitemata road policing manager Superintendent John Kelly said police would be looking at video footage and officers' reports to identify law-breakers but would not begin interviews for a few weeks.

Anyone who walked and cycled on the bridge was liable for a $250 fine. Police were also looking at the events that prompted people to move on to the motorway and some people could face other charges, he said.

Mr Kelly said there was just a "very small number" of protesters in question.

Getacross campaign spokesman Bevan Woodward said he thought it would benefit the cause if police did decide to press charges.

"It's an obvious travesty it's going to create some martyrs," he said.

Mr Woodward, who did not cross the bridge, said he was just as surprised as police when people did cross on to the motorway and it was unfortunate that police were caught out.

"We underestimated the determination of the people involved," he said.

Auckland Regional Council chairman Mike Lee and transport committee chief Christine Rose, who both walked up the bridge, said they believed the Transport Agency had relented and had authorised the police to let the public on.

"The police waved us through," Mr Lee said last night.

He admitted that was after "the cavalry" in the form of the first squadron of cyclists had led the charge, allowing "the foot-soldiers" to follow.

Mr Lee also suggested similarities with the Berlin Wall being brought down, noting that the campaigners were faced with a new "stalag-like" security fence before lining up along the Curran St on-ramp.

He said the agency could have avoided the disruption to traffic by agreeing to a request he and Ms Rose made in November for one lane to be barriered off for a walking and cycling trial on weekends and public holidays.

Ms Rose called the event "a joyous celebration of a structure that belongs to everybody."

Yesterday Mr Woodward was sitting at home with two 5kg bags of lollies that he had planned to dish out to protesters as a lolly scramble after Transport Agency regional manager Wayne McDonald denied them access to the bridge.

Instead the protesters refused to take Mr McDonald's "no" for an answer and stormed on to the motorway forcing authorities to close the northbound lanes for an hour.

The Getacross website registered another 400 people to the cause on Sunday taking the number of supporters to 10,900 members.