An emergency tornado warning was in effect early Sunday on the University of Oklahoma's Norman campus, officials said.

       The warning was posted at 1:22 a.m. on the school's official X account. The school issued additional warnings at 1:55 a.m and 2:02 a.m.

       "Seek shelter NOW inside the building you are in," the first message said. "Move to lowest floor/interior."

       The National Weather Service said it was watching for tornadoes throughout central and eastern Oklahoma early on Sunday. A small area within northwest Texas was also under watch, the agency's Storm Prediction Center said in an urgent update at 1:40 a.m.

       The center said about 15 minutes later that it had seen several "discrete supercells" that had "matured within the open warm sector across OK."

       "A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area," the center said. "Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings."

       There were also isolated chances of damaging wind gusts up to 70 mph and large hail, perhaps as big as about 2 inches in diameter, over some of the same area, weather officials said.

       This is a developing story. Please check back for updates.