A 42-year-old Australian man who allegedly posed as Justin Bieber online to solicit explicit images from children has been charged with more than 900 child sex offenses, police said Thursday.

Bieber, a 23-year-old Canadian pop singer, is currently in Australia performing his “Purpose World Tour.” Police have warned young fans and their parents to be extra vigilant when using the internet.

Gordon Douglas Chalmers, a law lecturer at the Queensland University of Technology in Brisbane, was charged in November with using Facebook and Skype to impersonate the star, after tip-offs from U.S. and German authorities. Chalmers was charged with using a carriage service to procure and groom children for sex and to access child pornography.

He was also charged with possessing child porn.

As a result of warrants issued in November to search his social media and messaging accounts and cloud servers, Chalmers was charged this week with another 931 child sex offenses dating back a decade, including rape and making child exploitation material, a police statement said.