Australian police have arrested 70 people and removed four children from their homes in a six-month nationwide investigation of a global child pornography network, officials said Thursday. Twenty other people have been summoned to appear in court. All 90 - including a police officer and several teachers - face charges of accessing images of child abuse on the Internet, police said. Australian Federal Police Commissioner Mick Keelty said the Interpol-led investigation was conducted simultaneously by law enforcement authorities in 170 countries. Further arrests are expected, he said. It was one of the largest child pornography investigations in Australian history, police said. The investigation was triggered after a hacker posted 99 child porn images on a European Web site, which attracted 12 million hits in just 76 hours, including 2,800 from Australian computers, police said.