HOUSTON -- Opponents of the Keystone XL pipeline project are resorting to physical obstruction to halt the project in the first signs of what could be a burgeoning civil disobedience movement against the line and the Canadian company building it.

TransCanada Corp. has broken ground on the southern leg of Keystone XL, having been awarded all the permits it needs and winning a lawsuit with a Texas landowner disputing the company's claim to eminent domain to obtain an easement to build on her land. The industry desires the pipeline as a means to free up a bottleneck in crude oil transport at the massive storage center in Cushing, Okla.

But opponents of the pipeline, which would carry oil from Canada's oil sands projects to Houston-area refineries, say they aren't backing down. They're now mobilizing through social media and organizing meetings to discuss new tactics and strategies and have taken their first public actions after losing legal options.

Yesterday activists claimed victory in a protest east of the Dallas-Fort Worth metroplex. A group of five protesters in Saltillo, Texas, chained themselves to equipment and put themselves between workers hired by TransCanada for the project and the wooded path they planned to clear to make way for Keystone XL.

"All the workers and all the police have just left the site," said Ron Seifert, spokesman for the group Tar Sands Blockade. "Everyone treated us very kindly, civilly, but here we are. It's a small victory for landowners and for everyone that has a legitimate grievance with this pipeline."

Both TransCanada and the protesters confirmed that yesterday's dispute was peacefully resolved. Local law enforcement was called in to warn the protesters that they were violating the law, but company spokesman David Dodson said management at the scene decided to stand down and move their crews to another location.

"We're working on two spreads in Texas, and they cover several hundred miles, and this was one piece of equipment on the right of way," Dodson said. "So it is correct that that crew did stand down."

Both sides in the dispute confirmed that they had not made direct contact with each other, and neither the company nor Tar Sands Blockade shows any signs of backing down. Seifert said the protesters had the landowner's permission to conduct their protest.

Late last month, north Texas landowner Julia Trigg Crawford lost her legal battle with TransCanada over the company's desire to lay a section of the pipeline across her land. Lamar County Judge Bill Harris upheld TransCanada's claim of eminent domain, condemning a small section of Crawford's land and seizing it for the pipeline project.

That decision led Tar Sands Blockade to spring into action. On Friday, a small group was arrested for locking itself to trucks being used to transport materials to construction sites. Organizers of that protest reported that those involved hailed primarily from the Midwest.

Yesterday marked the latest major action taken by the blockade movement, this time with protesters from the Houston and Dallas metro areas. Seifert said the team planned to try to block work at the same location again this morning. Opponents of Keystone XL argue that the pipeline, by increasing oil sands production, will exacerbate climate change problems. They also say oil derived from Alberta oil sands projects brings an increased chance of spills and serious pollution.

"I think the participants, the blockaders themselves, are at a point where they realize to do nothing is actually taking a greater risk than to rise up and take action," Seifert said. "We're just going to make sure that this job site stays secure and stays shut down."

Dodson of TransCanada said his company would move forward with planned construction as teams on the ground see fit. He said that his company was cooperating with law enforcement officials, and that the need for safety and restraint is being emphasized.

"We don't want anybody getting hurt," he said. Nevertheless, "work will continue."

A social network

The Tar Sands Blockade movement seems to be gradually growing in size and scope. Members are using Facebook and Twitter to communicate and advertise the location of events or planned rallies, such as a series of morning street protests in front of TransCanada's U.S. office in downtown Houston, according to Seifert.

A branch of the protest effort, Tar Sands Blockade-Houston, is organizing a training seminar for volunteers next week. A Facebook posting by the group invites opponents of Keystone XL to partake in "non-violent direct action training" aimed at shutting down construction of the project.

Though only five participated in the Saltillo protest yesterday, Seifert says Tar Sands Blockade is growing fast, thanks largely to Web communication. He estimated a few hundred had signed up to be part of his team's movement so far.

Bold Nebraska, a group fighting the largest planned leg of Keystone XL in that state, has voiced support for the Texas group's efforts. It also voiced opposition to a modified route for the pipeline through Nebraska that TransCanada announced yesterday. The group says a lawsuit it's supporting that challenges the process that the state is relying on to approve the route will have its first hearing Sept. 14 in Lancaster County.

TransCanada says the process afforded ample time for public comment and consideration.

"The preferred alternative route in this Supplemental Environmental Report was developed based on extensive feedback from Nebraskans and reflects our shared desire to minimize the disturbance of land and sensitive resources in the state," company CEO Russ Girling said in a release.

The company estimates that the Gulf Coast project -- the part of Keystone XL running from Cushing to Houston-area refining centers -- is a $2.3 billion investment that will generate about 4,000 jobs. The entire project, should the Obama administration approve an international border crossing request, will cost about $5.3 billion.