Taiwanese singer Nine Chen, whose Covid-19 test came back positive on Thursday (June 3), had been in a dance rehearsal just the day before with three bandmates from Wolf(s).

While Chen, 34, was sent by ambulance to a quarantine hotel, the other three - Taiwanese singers Lai and Wayne Huang, and Singaporean Kenny Khoo - are self-isolating at home. A fifth member of the band, Shou, was not at the rehearsal.

In a lengthy Instagram post on Thursday, Chen apologised for being "thoughtless" and the troubles caused to those he had come into contact with.

The popular singer of hit song Werewolves, a collaboration with Khoo, also posted a video with a timeline, saying that he experienced breathing difficulties on May 27 and had gone to a clinic two days later.

A test on May 31 came back negative and an X-ray showed that his lungs were fine, he added, noting that he was given medicine for allergies.

The decision was made to proceed with the rehearsal on Wednesday (June 2) for an upcoming music video in July Everyone, including the dance instructor, wore masks to be safe and also made sure that no Covid-19 rules were broken.

Chen, who is one of the hosts of long-running variety show 100% Entertainment, said he was feeling a bit tired and had some cold symptoms, but was otherwise fine.

"I did something wrong. I also remind everyone not to take any symptoms lightly. Just stay at home if you don't need to go out."

Using his own case as an example, he added: "If you have serious symptoms, go for a test. Wait until the test is confirmed negative before going out. I wish you all safety and health."