Several people have reported experiencing eye pain, vision problems, and sunburnt skin on Sunday after attending ApeFest, a Bored Ape Yacht Club NFT collection event in Hong Kong that ran from November 3rd-5th.

Some ApeFest attendees posted on X (formerly Twitter) after seeking medical attention, with one person reporting that they had been diagnosed with Photokeratitis — aka, “welder’s eye,” a condition caused by unprotected exposure to ultraviolet radiation — and another saying the issue was a result of UV from the stage lights, leading to speculation that the injuries were caused by improper lighting used at the event.

“I woke up at 04:00 and couldn’t see anymore,” said @CryptoJune777. “Had so much pain and my whole skin is burned. Needed to go to the hospital.”

Yuga Labs, the blockchain company behind the Bored Ape Yacht Club NFT project, says it’s aware of the situation and taking the reports seriously. “We are actively reaching out and in touch with those affected to better understand the root cause,” said Yuga Labs spokesperson Emily Kitts in a statement to The Verge. “While we don’t release event attendance numbers, based on the inbounds we have received, our current estimate puts the percentage of people affected at much less than 1 percent of those working and attending our Saturday night event.”

Similar symptoms, which include sunburn and waking up to severe, burning eye pain, were reported in 2017 by partygoers who attended a Hypebeast event at The Landmark commercial complex also in Hong Kong, with the event’s DJ later discovering lighting used mainly for disinfection purposes had been installed at the venue. The Landmark venue did not feature on the ApeFest event plan, and the two incidents appear unrelated.