CINCINNATI (AP) - An Ohio coroner says her office lacks evidence to make any conclusions on what caused the fatal brain damage that killed a 22-year-old U.S. college student who had been detained more than a year by North Korea.

Dr. Lakshmi Sammarco says "the bottom line" is examination couldn't determine what happened to Otto Warmbier. Her office's newly released report says his brain was damaged by oxygen deprivation, but it's not known what triggered that.

His parents and President Donald Trump have accused North Korea of torturing him. North Korea has denied mistreating Warmbier, who was arrested in January 2016 for allegedly stealing a propaganda banner while visiting with a tour group.

He died in June 2017, less than a week after his return to Cincinnati.