Doctors say there were no obvious signs of physical trauma or evidence of bone fracture but Warmbier's family insists he had been physically abused by his captors.
Doctors at the Cincinnati Medical Center, where Mr Warmbier was treated following his return to the USA on 13 June, determined he suffered from "unresponsive wakefulness", also known as persistent vegetative state, due to "severe neurological injury".
Warmbier was arrested while visiting as a tourist and accused of trying to steal an item bearing a propaganda slogan, according to North Korean media.
Seoul's Defence Ministry said the bombers engaged in routine exercises with South Korean fighter jets aimed at showing deterrence against North Korea.
The Republican lawmakers were not alone in their anger, as President Trump called the Warmbier family's ordeal a "terrible disgrace".
Warmbier's parents said they believe their son was subjected to "awful, torturous mistreatment" by the North Korean regime. And frankly, if he were brought home sooner, I think the result would have been a lot different.
"I think the first objective has to be to get the three other Americans out, and get a full explanation of what happened to Otto Warmbier". Warmbier, an American college student who was released by North Korea in a com. "At least I know China tried", Trump wrote on Twitter.
President Moon Jae-in on Monday said he wants to bring North Korea to the negotiating table this year.
Warmbier was detained by the North Korean regime a year ago and returned home with extensive brain damage last week.
In an interview with the Washington Post released on Wednesday, the South Korean president said that the issue is not that simple, noting that the deployment must go through due process in South Korea. "While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out", he wrote, referring to his apparently failed attempts to persuade the Chinese government to contain the totalitarian regime, with whom China shares a 880 mile-long stretch of border.