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LAS VEGAS — Supporters, some of them armed, rallied Saturday around Cliven Bundy in his showdown with U.S. rangers over cattle grazing on federal land, forcing a temporary shutdown of northbound lanes of Interstate 15 near his ranch, the Nevada Highway Patrol said Saturday.

The highway was reopened early Saturday afternoon after protesters moved to the side of the road and stopping blocking it. But traffic was backed up for three miles in both directions, Trooper Loy Hixson told CNN.

Hixson said no one in the armed crowd has threatened violence, but a U.S. senator acknowledged that “tensions are still near the boiling point.”

Authorities dispatched a SWAT vehicle to the protest site at Bunkerville, about 80 miles northeast of Las Vegas, according to photos provided by KTNV.

The large gathering was expected Saturday by the Bundy family, who told reporters a day earlier that many supporters couldn’t attend the weekday protest because of work.

The growing protest came amid the U.S. Bureau of Land Management’s decision to put an early end to a roundup of Bundy’s cattle, which the feds claim have been illegally grazing on federal land for 20 years.

The bureau cited public safety concerns for abruptly ending the weeklong roundup.

The Old West-style controversy — centering on a family that has been ranching in Nevada since the 1800s — drew armed militia groups from across the country to the cattleman’s side this week, especially after a YouTube video captured a tussle teetering on violence between rangers and protesters.

“Based on information about conditions on the ground, and in consultation with law enforcement, we have made a decision to conclude the cattle gather because of our serious concern about the safety of employees and members of the public,” said Neil Kornze, director of the U.S. Bureau of Land Management.

Kornze was just confirmed to the directorship this week by the U.S. Senate.

U.S. Sen. Dean Heller, R-Nevada, appealed for calm Saturday and told out-of-state supporters to return home.

“The dispute is over, the BLM is leaving, but emotions and tensions are still near the boiling point, and we desperately need a peaceful conclusion to this conflict,” Heller said in a statement. “I urge all the people involved to please return to your homes and allow the BLM officers to collect their equipment and depart without interference.

“We are very close to a calm, peaceful resolution but it only takes the action of one individual to stir things up again and bring us back to the brink of violence and no one wants to see that happen,” Heller said.

In his Saturday announcement, Kornze said that contracted wranglers and U.S. rangers apparently made enough progress in rounding up cattle that belonged to Bundy, who is challenging federal authority in a valley that his family settled in the Wild West era.

The roundup occurred near the scenic Virgin River at Bunkerville, where Bundy’s ranch is located.

“We ask that all parties in the area remain peaceful and law-abiding as the Bureau of Land Management and National Park Service work to end the operation in an orderly manner,” Kornze said in a statement.

“After one week, we have made progress in enforcing two recent court orders to remove the trespass cattle from public lands that belong to all Americans,” Kornze said.

He was referring to how two different federal judges ordered the removal of Bundy’s cattle, which officials say have been illegally grazing on federal land for 20 years.

Bundy owes the U.S. government more than $1 million in unpaid grazing fees, bureau officials said.

Bundy’s dispute with the government began around 1993 when the bureau changed grazing rules for the 600,000-acre Gold Butte area to protect an endangered desert tortoise, CNN affiliate KLAS reported.

Bundy, who’s in his 60s, cites the Constitution in asserting that the state of Nevada holds sovereignty over the charging of grazing fees and, if he owes such a fee, he would pay it only to the local government — not to the feds.

Bundy also contends his family has been ranching in the Virgin Valley on the Nevada range since 1877 — long before the Bureau of Land Management even existed and before the tortoise was declared endangered.

In recent days, the number of cattle rounded up on U.S. lands slowed to one or two dozen a day, according to bureau figures.

From March 5 to Friday, authorities impounded a total of 389 cattle, the Bureau of Land Management said. Officials gathered 12 head of cattle Friday and 25 Thursday, the bureau said.

Bundy has said he owns 500 of the more than 900 cattle that federal officials are planning to confiscate for illegal grazing, according to local media accounts, with each head worth about $1,000.

The rancher couldn’t be immediately reached for comment Saturday after the feds shut down the roundup.

On Wednesday, a scuffle between protesters and federal rangers was videotaped.

Bundy family members and their supporters confronted the rangers and angrily told them to leave Nevada. Fearing that the cattle were being killed in the roundup, they also demanded to know why a backhoe and dump truck was being used, but federal officials later said the equipment was used to restore the range.

For their part, federal rangers held Tasers and barking dogs on leashes during the faceoff.

Federal officials say a police dog was kicked and officers were assaulted. Bundy family members say they were thrown to the ground or jolted with a Taser.

In the end, the rangers got into their white SUVs and drove away, a YouTube video of the incident showed.

The incident is under federal investigation.

Several armed militia groups from around the country then joined the Bundys in their showdown.