HAWAII — Hundreds of people staged a major protest on a Hawaiian mountain on Wednesday to stop the construction of a gigantic scientific instrument.

Their target: the Thirty Meter Telescope (TMT). Once built, it will be the largest optical observatory in the world, with a light-gathering mirror that spans nearly 100 feet.

A multinational group of astronomers behind the project thinks Mauna Kea's 14,000-foot summit is the perfect spot for a telescope — far away from any light pollution or cloud interference.

But many native Hawaiians consider the location sacred ground. The new observatory, some natives say, would desecrate the area.

Protesters marching up Mauna Kea told Business Insider it was time to halt development on the mountain, where 13 other telescopes already sit.

Construction on the telescope began in April, but a large protest postponed the work for two months and led to more than 30 arrests.

On Wednesday, Hawaiian officials allowed TMT to resume construction. But hundreds of protesters again stormed the mountain to halt a small caravan of construction vehicles attempting to reach the summit. Some demonstrators told us they camped on the roadside to ensure the trucks would not slip by under cover of night.

The caravan of trucks trying to drive up the mountain. Kelly Dickerson/Business Insider

The plan, according to Earl DeLeon, one of the protest leaders, was to eventually allow the trucks to pass. But multiple lines of people farther up the mountain slowed down the process.

The trucks inched along the 8-mile journey to the summit, while demonstrators sang, blew conch shells, and waved Hawaiian flags.

A protester blares a conch shell. Kelly Dickerson/Business Insider At least one man was arrested before we arrived on the scene, but details were unclear. Officers told Business Insider only that he was being taken to the Hilo police station.

Once the trucks neared the end of the paved road, where a steeper gravel access road to the summit begins, police officials issued a warning that anyone who obstructed the path of the trucks would be arrested. The protesters were permitted to walk along the shoulder of the path to the mountain, but they couldn't directly block the road.

"I want to do this peacefully; honestly, I don't want to arrest anyone," a lieutenant of the Hawaii Police Department told the crowd through a loudspeaker.

Several people farther up the mountain seemed to defy the warning, saying they hadn't heard the announcement. So officers were forced to stop and blare it again and again.

Protesters ahead of the caravan pulled big rocks onto the access road and bad weather rolled in, forcing the police and Department of Land and Natural Resources (DLNR) officers to turn around after the nearly seven-hour-long demonstration.

Police made at least 11 arrests on Wednesday, according to MauiNow.com.

"From myself I apologize to you guys," Lino Kamakau, branch chief officer with DLNR Hawaii County, said through tears. "I hope you guys understand what I gotta do. Our number one thing right now is public safety. We're not going up."

The construction trucks made it less than two miles up the gravel access road.

TMT officials spent years securing all the necessary permits to build on a preservation and speaking with native Hawaiians about their concerns. There are no legal issues stopping the construction of TMT, Gov. David Ige of Hawaii has said. (They have other problems, though.)

"It is our belief that there will be mutual respect and aloha on Wednesday and in the days ahead as TMT restarts construction of the Thirty Meter Telescope," Ige said in a statement issued Tuesday. "TMT has the approvals needed to proceed with construction. We respect those who oppose the project and their right to peaceably assemble and to protest in an orderly and civil manner."

Many protesters said they planned to return to the mountain Thursday.