MANDAN, N.D. (AP) – North Dakota authorities say work at several Dakota Access pipeline construction sites was temporarily stopped Wednesday because of protesters.

The Morton County Sheriff’s Office says authorities blocked County Road 136 near St. Anthony and advised protesters they couldn’t drive through.

Officials say area residents were alerted and a school in St. Anthony was put on lockdown. Authorities say officers were concerned that the traffic would interfere with emergency response to the community.

Also Wednesday, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit heard arguments in the Standing Rock Sioux Tribe’s request to continue blocking work on a section of the pipeline near Lake Oahe (oh-AH’-hee) while the tribe seeks to appeal a lower-court ruling from September.