Greenpeace environmental activists light flares on the European Council Europa building | Olivier Hoslet/EFE via EPA Security questions as Greenpeace activists scale EU summit building 57 activists were arrested, according to Brussels police.

Nearly 30 Greenpeace activists scaled the building where EU leaders are due to meet later Thursday — hanging a large banner, lighting red distress flares and sounding a loud fire alarm.

They used a vintage red fire engine with a long ladder to reach the building.

Security in the area around the European Council's buildings is high ahead of the regular gatherings at which all EU leaders typically attend along with an army of diplomats and advisors. Roads are blocked and scores of armed police are in place to enforce a ring of steel around the summit building that only accredited people and vehicles can enter.

The full security arrangements were not in place around 6 a.m. on Thursday morning when Greenpeace activists were able to climb up the face of the Europa building where leaders will meet this afternoon inside the iconic inner lantern (or the "space egg" as it is widely known in Brussels.)

An EU official played down the breach and claimed it would not affect the meeting. “The security of the building was never at risk. It will not impact the summit.” Responsibility for the security perimeter around the building lies with the Belgium police, according to the official.

Council security staff apparently did not realize what was happening until activists began scaling the building, according to Greenpeace EU’s spokesperson Mark Breddy. But when they did, local Brussels police and fire services were called in to intervene.

At noon, six hours after the demonstration began, the EU Council press office tweeted that the demonstration was over and the summit would continue as planned. The EU summit officially begins at 3 p.m. local time.

Those involved have been peacefully removed from the building, as has the banner. Twenty-nine people involved in the climb were arrested, as well as 28 activists on the ground, according to local authorities. They were taken to a local police station just before noon. They could face administrative sanctions, including a fine, but it is up to a public prosecutor to decide on the charges.

Sixty-one activists in total from seven countries participated in the demonstration, according to a Greenpeace press release. The plan had been in the works for some time, according to Breddy.

With EU leaders set to discuss climate change during the EU summit, Greenpeace’s main message is for a more aggressive EU climate target by 2030. "The reason we did this is to say that climate neutrality 30 years from now is not enough," said Breddy. The group is instead calling for emissions to be cut by 65 percent rather than the current target of at least 40 percent emissions reductions by 2030.

Louise Guillot contributed reporting.