Upon announcing the investigation the IOC suspended qualifying for the 2020 boxing tournament -- making it the only sport not to have its qualifiers approved -- and warned that it could be stripped of the right to run the competition.
American Wilder retained his WBC belt after a thrilling 12-round battle ended in a split decision draw.
The 33-year-old Singh, a bronze medallist at the 2008 Beijing Olympics, has an unbeaten 10-0 record since he turned pro in 2015, but failed to get a single fight this year.
Adonis Stevenson's doctor Alexis Turgeon said it was "too early to comment" on the fighter's long-term prognosis, but it was likely he would have lasting neurological damage.
The Haitian-born boxer, 41, was admitted to the hospital on Saturday after the unbeaten 31-year-old Gvozdyk finished him off with a crushing right hand.
Stevenson was dominated almost from beginning to end by Gvozdyk, who sent the Canadian champion reeling before landing his knockout blow in the 11th.
Wilder had Fury on the canvas twice, including a spectacular final round knockdown, but was unable to get the knockout victory he had promised to deliver at the Staples Center.
On Friday, the IOC said it was halting preparations for boxing at the 2020 Games and launched a probe into the sport's troubled governing body -- the International Boxing Association (AIBA).
Defending champion Wilder takes on British challenger Fury at the Staples Center on Saturday in an eagerly-anticipated collision of unbeaten heavyweights.
The IOC stressed that it still wanted boxing to go ahead at Tokyo 2020 but said its inquiry into the International Boxing Association "can lead to the withdrawal of (its) recognition".
The island nation is a super-power in boxing, having won almost half of its 78 summer Olympic gold medals in the sport.
The 27-year-old Bivol cruised to victory in the third defense of his title as he won almost every round against the heavy underdog Pascal. Two judges scored it 119-109 and the other had it 117-111 in favor of Bivol.
The 35-year-old beat Ukraine's Hanna Okhota 5-0 in the final of the 48kg category contest in front of an electric home crowd.
The Indian beat North Korea's Kim Hyang Mi to reach the 48kg final where the 35-year-old overcame her opponent in a unanimous decision of the five judges in the semifinals.
Veteran trainer Roach and Pacquiao split abruptly after a 16-year partnership following the Filipino's defeat to Jeff Horn in 2017.