A HOAX e-mail circulating in Hong Kong and around the world is warning mobile phone users their handset will be destroyed by a 'virus' if they answer certain calls. The message - which claims the alert has been sanctioned by manufacturers Nokia and Motorola - says three million phones in the United States have been rendered useless by the bug. But officials say the scare is nothing more than a hoax, thought to have started in the Middle East, and is similar to an anonymous message sent to local mobile users last year saying phones were at risk of being 'infected'. The e-mail says users must not answer a call if the screen shows that the number of the caller is 'unavailable'. 'If you answer the call, your phone will be infected by a virus,' it says. 'Don't answer the call. End the call immediately. This virus will erase all information from both your phone and your SIM card, which will make your phone unable to connect with the telephone network - you will need to buy a new phone.' The message was originally received by an employee of Telstra, Australia's biggest phone network, and he forwarded it to friends. Telstra says the message is a trick and must be ignored. 'It's been proven as a hoax,' global project manager Sam Irani said from Sydney. 'We sent it internally to be checked out, but it's not true.' Kay Yau Ka-yee at the Office of the Telecommunications Authority said phone manufacturers and network operators in Hong Kong had been asked about the e-mail and none believed it was possible for a virus to wipe out phone information. 'We concluded that this is just a rumour. The person doesn't mention how he knows this, why it would happen or who he is,' she said. Ms Yau said the companies said a handset would never display the word 'unavailable' when it rang. Motorola Hong Kong's general manager of operations Cedric So Wai-hong said his company had not confirmed the information in the e-mail and believed it to be a prank. 'There's a guy in the Middle East who was upset with a network operator and he sent out an e-mail last year,' he said. 'A lot of people turned off their phones when they read it, but it was kind of a joke.' A Nokia spokesman in Hong Kong said: 'Spreading a virus to a handset over the air is not possible. 'We take these claims seriously and will continue the investigation of this issue.' Nokia in Singapore said that while the warning was baseless, 'that's one of the dangers of e-mail - everyone passes it around so it's going to keep resurfacing from time to time'.