Warmbier's father had also blasted the Obama administration for not doing more.
Doctors there said they found no traces of active botulism, a toxin that can cause nerve injury.
Warmbier died Monday of severe brain damage, which doctors said was likely due to cardiopulmonary arrest.
Four years ago, Otto Warmbier graduated from Wyoming High School, where he took to the podium in front of his classmates, to wish them luck as they moved onto their next step in life.
Warmbier was returned to OH on June 13 after being held for more than 17 months.
Warmbier's brother and sister spoke at Thursday's memorial, as did a number of his friends, said attendee Fred Koss.
In March 2016, Kim Dong Chul, a 62-year-old Korean-American missionary, was sentenced to 10 years of hard labor for subversion.
His family had no news of him until 13 June, when Pyongyang said he had been in a coma since his trial after contracting botulism and receiving a sleeping pill.
Kenneth Bae, the U.S. citizen detained by North Korea for two years, says he believes it is possible the late Otto Warmbier could have been tortured during his captivity in the communist country.
This flies in the face of a tweet from Tillerson's boss, US President Donald Trump, that has caused a great deal of hand-wringing: "While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out".
Inside the arts center, some of the personal items Warmbier took to North Korea were on display: a wallet, a University of Virginia notebook and the cream-colored linen blazer he wore there, CNN says. His eyes opened and blinked but he showed no indication that he understood verbal commands or was aware of his surroundings.
'To do otherwise would just be an insult to Otto, knowing that he always wanted to see others fly, ' she said.
Warmbier was traveling in North Korea with a tour group, and was arrested at Pyongyang airport as he was about to leave.
The commentary talked about how Trump might "launch a preemptive strike on North Korea to distract from domestic political problems" and used the example of how Bill Clinton launched a military attack on Iraq while being investigated for his sex scandal.
Three South Korean nationals were detained in North Korea during their missionary work since 2013, and the remaining three South Koreans are North Korean defectors who returned and are in custody, a legislator briefed by the South Korean spy agency told reporters last week.