The Chinese gay app Blued has put a seven-day hold on new registrations after reports that underage users contracted HIV on dates they set up via the app, CNN Business reports.

Blued says it has more than 40 million users worldwide, making it the world’s largest networking app for the global LGBT population, according to Reuters. Two thirds of these users are in China, which has a flourishing gay community.

According to the financial magazine Caixin, the app is popular among gay teenagers, many of whom were having unprotected sex via hookups set up on the app. They were also sharing pictures and hosting livestreaming events.

Blued does not allow underage users to pose as adults 18 years old and older, whether they are texting, posting photos or livestreaming. “Blued always forbids juveniles from logging on and using the app,” the company said in a statement, according to Reuters.

As a result of the HIV reports, Blued not only stopped signing up new users but also launched an audit to figure out how to crack down on youth using the app.

The company said it already supports HIV prevention and education. “What we have done on AIDS prevention is seen by all,” the founder and CEO Ma Baol told CNN. “We probably are the best, and we have done the most. Our priority now is to supervise and examine our content.”

Blued is backed by state-run Beijing News. CNN reports that the app was founded by a former police officer and has been accused of growing so fast that it hasn’t protected underage users. For example, a Chinese researcher reported that high school students said they had been pressured into have sex with older men they met on the app.

In related news, the number of people in China living with HIV/AIDS grew 14 percent between June 2017 and June 2018, an increase of more than 100,000. Most cases were attributed to sex. In total about 820,000 people are estimated to be living with the virus in the country. For more details, click here.

In comparison, the U.S. Centers for Disease Control and Prevention estimates that about 1.1 million people are living with HIV in the United States.