AUSTIN (KXAN) — Twenty-two Greenpeace USA activists created a blockade on the Fred Hartman Bridge in Baytown, Texas early Thursday ahead of the third Democratic primary debate in Houston.

Eleven of those climbers are dangling over the side of the bridge, an activist said in a Facebook Live video. The climbers held colorful ribbons and streamers to block traffic under the bridge.

The group aims to “shut down the largest oil export channel in the U.S.” for 24 hours.

Law enforcement officials told the local NBC affiliate that Houston Ship Channel was temporarily closed down because the protesters threatened to lower themselves to stop ship traffic.

“This climate emergency was fueled by Trump’s climate denial and the oil industry’s greed,” the group wrote in the Facebook posts. “We’re here to resist.”

Harris County constables are on the bridge monitoring the scene. Law enforcement officials told local media that the protesters were peaceful so far. At least two lanes of the bridge were also blocked to traffic and they are expected to remain blocked until the protest is over.

Authorities said they had no prior knowledge of the protest.