TULSA, Okla. (AP) — Officials on Saturday warned some Tulsa residents to prepare to head to higher ground because old levees holding back the swollen Arkansas River are stressed and more rain is expected for the flood-weary region.

The river was four feet above flood stage on Friday and was already causing flooding in parts of Oklahoma's second-largest city, including in south Tulsa where the murky brown water had inundated low-lying neighborhoods and crept right up to the River Spirit Hotel and Casino, which closed for the weekend.

City officials said at a news conference Saturday that people...