Following the news that 70 South Korean nationals who attended CES 2022 in Las Vegas tested positive for the virus upon their return home, the organizers of the world’s largest technology show said Thursday that they are unable to confirm the total number of COVID-19 cases that were contracted at the in-person event.

“We don’t have confirmation of the number of cases as it is extremely difficult to determine exactly when and where anyone contracted COVID-19,” a spokesman for CTA (which organizes CES) told Consumer Electronics Daily.

Those who tested positive include representatives from Samsung Electronics and Hyundai Motor, sources told Reuters. Hyundai Heavy Industries, meanwhile, said that six of its employees who attended CES tested positive while in the U.S. and were quarantined, with some now having been released.

“Many Korean business people who attended CES […] are now confirmed to be infected with COVID-19,” Son Young-rae, a senior South Korean health ministry official, said in a briefing. “We are promptly contacting those who participated in the event and conducting epidemiological investigations, but we urge domestic businesspeople or those who are in Korea that attended the event to undergo PCR tests as soon as possible.”

Related: 70 South Korean Nationals Caught COVID-19 At CES 2022

The wealth of cases could have an impact on the rest of South Korea, which had just brought down daily case numbers by restoring a variety of tough social distancing rules and widely adopting vaccine passports at public locations.

Of the 40,000 people who attended CES, 30 percent are estimated to have traveled from outside the United States, including Stellantis CEO Carlos Tavares, who the company said did not contract the virus.

Read Also: GM Pulls Out Of CES 2022 Amid COVID Omicron Concerns, Silverado EV To Debut Online

CES organizer Consumer Technology Association said that the testing it did at the show was reported to the local Southern Nevada Health Authority. Earlier this week, the state’s health authorities said that many of those with new cases had traveled recently and visited numerous locations “where they could potentially have acquired their infection.”

Although CES was intent on running its show in person, a number of companies pulled out at the last minute as a result of the Omicron variant, including General Motors and Amazon.