CANON BALL, N.D. -

Twenty-eight protesters against the Dakota Access oil pipeline were arrested west of Mandan, North Dakota, during a day in which activists held demonstrations nationwide.
    
Morton County sheriff's spokesman Rob Keller says about 400 protesters put a pickup truck and tree branches on BNSF Railway tracks Tuesday near a pipeline work staging area. The railroad says trains were delayed three hours.
    
Officers in riot gear used pepper spray and in one instance a stun gun against protesters who refused to leave.
    
Activists called for demonstrations at Army Corps of Engineers offices and at banks financing the pipeline construction. Protests were reported across the country, from California to Vermont.
    
The $3.8 billion pipeline is to carry North Dakota oil to a shipping point in Illinois. Opponents worry it will harm the environment.
    
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11:45 a.m.

Hundreds of protesters against the Dakota Access oil pipeline gathered outside a work staging area west of Mandan, North Dakota, and disrupted freight train traffic.
    
Morton County sheriff's spokesman Rob Keller says protesters on Tuesday morning put a pickup truck and tree branches on BNSF Railway tracks. It wasn't immediately clear how many trains were affected.
    
Officers in riot gear responded. There were no immediate reports of arrests.
    
Mandan is about 50 miles north of a camp where hundreds of protesters have gathered in recent months to oppose the $3.8 billion pipeline that's to carry North Dakota oil to a shipping point in Illinois.
    
Robert F. Kennedy Jr. was slated to visit the camp later Tuesday. He's an environmental attorney and president of Waterkeeper Alliance, which seeks to protect watersheds worldwide.
    
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10:55 a.m.The company building the $3.8 billion Dakota Access pipeline is seeking a federal court's permission to lay pipe under a Missouri River reservoir in North Dakota and finish the four-state project.
    
The Army Corps of Engineers called Monday for more study and input from the Standing Rock Sioux before it decides whether to allow the pipeline to cross under Lake Oahe. The tribe says the pipeline threatens drinking water and cultural sites.
    
Dallas-based Energy Transfer Partners and a subsidiary are asking U.S. District Court in Washington, D.C., to confirm the company has the legal right to proceed.
    
The Corps in July granted ETP the permits needed for the crossing, but it said in September that further analysis was warranted given tribal concerns.
    
ETP says additional delay amounts to politic interference.

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The company building the $3.8 billion Dakota Access oil pipeline is denouncing a decision by the Army Corps of Engineers to delay an easement to cross a Missouri River reservoir in North Dakota.
    
Energy Transfer Partners CEO Kelcy Warren said in a statement Monday that the decision is "motivated purely by politics at the expense of a company that has done nothing but play by the rules."
    
The Corps wants more studies and tribal input before it decides whether to allow the pipeline to cross under Lake Oahe. The Standing Rock Sioux says the pipeline threatens drinking water and cultural sites. Protests have been ongoing for months.
    
ETP says it will "vigorously pursue its legal rights."
    
The 1,200-mile pipeline from North Dakota to Illinois is largely complete outside of the river crossing.
    
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8 a.m.
    
The Standing Rock Sioux chairman says the decision by the Army Corps of Engineers to delay an easement for the $3.8 billion Dakota Access pipeline indicates protests against the project are succeeding.
    
The Corps said Monday it needs more studies and tribal input before it can decide whether to allow the oil pipeline to cross under a Missouri River reservoir in North Dakota. The tribe says the pipeline would threaten drinking water and cultural sites. Protests against its construction have been ongoing for months.
    
Chairman Dave Archambault said in a statement that the Corps' decision is encouraging and shows the demonstrations are bringing the tribe's concerns to light.
    
An industry group supporting the pipeline criticized the Corps' decision. The MAIN Coalition called it an attempt at "death by delay."