SYRINGA, Idaho — A Native American tribe and a conservation group have filed a joint suit in federal court to halt a massive shipment of oil field equipment that was traveling late Thursday through a federally protected river corridor in northern Idaho. The megaload moved past a group of about 50 protesters Thursday night at Syringa and continued its journey toward Canada, The Lewiston Tribune reported. Protesters have dogged the load since it started its trip Monday night and more than two dozen demonstrators have been arrested. The terms of the rig’s permit from the Idaho Transportation Department allow it to travel only at night along U.S. Highway 12. Late Thursday afternoon, Idaho Rivers United and the Nez Perce Tribe asked the federal court in Boise to halt the 225-foot-long load now in the Clearwater-Lochsa Wild and Scenic River Corridor and block the movement of other planned megaloads over that route. Bill Sedivy of Idaho Rivers United served notice of Thursday’s lawsuit on the rig’s driver but the load kept rolling. The lawsuit asks the court to order the Forest Service “to enforce its already established jurisdictional authority over the use of U.S. Highway 12 within the Nez Perce-Clearwater National Forest and Wild and Scenic River corridor” by prohibiting megaloads until the agency completes a corridor impacts study and consultation with the tribe. The Forest Service “is sending a terrible message to anyone who would abuse rivers and forests, as well as important cultural and historic sites on our public lands,” Sedivy said in a statement. Nez Perce tribal chairman Silas Whitman said the tribe had exhausted diplomatic options. The conservation group filed a federal lawsuit in 2011 accusing the Forest Service of neglecting its duty under the 1968 Wild and Scenic Rivers Act to protect the corridor when ExxonMobil Corp. sought to move big, heavy equipment up the roadway. In February, a federal judge sided with IRU, concluding forest supervisors have authority to review state-issued travel permits for over-legal loads. On Monday, Nez Perce-Clearwater National Forest Supervisor Rick Brazell sent a letter urging shipper Omega Morgan to delay the load until agency officials could review travel plans and consult with tribal leaders. Forest Service officials said earlier this week they were taking a wait-and-see approach. Olga Haley, a spokeswoman for Oregon-based Omega Morgan, has said the company is committed to doing its job professionally and with what it believes are the appropriate permits. Montana has also granted permission for the material to pass through that state. The 225-foot-long load — a large water purification unit — is being hauled to Alberta, Canada, for an oil sands project. The load is 21 feet wide and weighs 644,000 pounds. Omega Morgan wants to move at least nine of the large loads along the two-lane route.