Fifty-five people were arrested in Washington during a protest Friday against the proposed Keystone XL pipeline, which opponents contend would encourage exploitation of Canadian oil sands and contribute to environmentally damaging climate change.

The protesters targeted offices of Evironmental Resources Management in the 1700 block of I Street NW, a consulting firm hired by the State Department to assess the proposed pipeline’s environmental impact.

Pipeline opponents say ERM’s analysis — which concluded that the project would have no significant environmental effect — is deeply flawed.

Police said the demonstrators entered the lobby of the office building about noon and were told numerous times to leave. After they declined to follow police orders, they were arrested on a charge of unlawful entry, police said.

Organizers said the demonstration was part of a campaign called “Summer Heat,” noting that the last half of July is statistically the year’s “hottest stretch.” In a touch of irony, the protest came on one of July’s most pleasant days, one distinguished by below-normal temperatures and uncommonly low humidity.