Two people were arrested Dec. 6 at a pipeline protest in West Texas, bringing an intensifying political battle against oil and gas infrastructure to a state where the energy industry typically enjoys wide support.

About 40 protesters gathered outside the construction site of Energy Transfer Partners' (NYSE: ETP) Trans-Pecos pipeline near Alpine, Texas, on the morning of Dec. 6, and three locked themselves to the gate surrounding the site, according to Lori Glover, a member of the Big Bend Defense Coalition, which organized the event.

The group intended to slow down construction, said Glover, who said she was arrested, along with one other protestor, for criminal trespassing.

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A spokeswoman for the Brewster County Sheriff's office said the protesters were detained, not arrested.

Energy Transfer Partners is also constructing the embattled Dakota Access Pipeline, which for months has been protested by the Standing Rock Sioux tribe and others who are concerned that a spill could contaminate drinking water. The line was further delayed on Dec. 4 when the U.S. Army Corps of Engineers denied the company a permit to drill under a North Dakota lake.

A representative from Energy Transfer Partners did not immediately respond to a request for comment.

Protesters in West Texas also cited concerns over water contamination. Glover said the group was concerned about the Rio Grande River, which the pipeline would cross, and other watersheds.

The Trans-Pecos pipeline is a 148-mile joint venture with the Comisión Federal de Electricidad, Mexico's federal electricity commission. The line, expected to move 1.4 billion cubic feet of natural gas per day, will originate outside Fort Stockton, Texas, and deliver gas to the U.S.-Mexico border, where it will connect with a gas line that is currently under construction.

Opposition to the Trans-Pecos line dates back two years, Glover said. Groups such as the Big Bend Conservation Alliance have sought to halt the line by advocating to stop Energy Transfer's use of eminent domain, which allows the company to seize private land for construction.

Texas—home to vast shale basins such as the Eagle Ford and Permian, which support the state's economy—does not typically face the same opposition to oil and gas development as many other states, such as New York, which has banned hydraulic fracturing.