BISMARCK, N.D. — A New York woman seriously hurt protesting the Dakota Access oil pipeline faces multiple surgeries and could lose an arm, her father said Tuesday, and protesters and law enforcement gave conflicting accounts about what might have caused the explosion that injured her.

Sophia Wilansky, 21, was listed in serious condition and was undergoing surgery at a Minneapolis hospital.

Wilansky’s father, Wayne Wilansky, said his daughter was hurt when law enforcement threw a grenade. The Morton County Sheriff’s Office maintains authorities did not use concussion grenades or any devices that produce a flash or bang during a clash late Sunday and early Monday near the camp along the pipeline route in southern North Dakota where protesters have gathered for months.

The sheriff’s office suggested in a statement Monday that an explosion heard during the skirmish might have been caused by small propane tanks that authorities said protesters had rigged to explode.

Dallas Goldtooth, a protest organizer with the Indigenous Environmental Network, did not immediately respond to a request for comment Tuesday. Wayne Wilansky disputed the claim by authorities, saying “there’s multiple witnesses and my daughter, who was completely conscious, said they threw a grenade right at her.”