Detectives are investigating possible links between a series of threats against Secretary for Housing Dominic Wong Shing-wah. Sau Mau Ping detectives tracing the senders of letters threatening to poison Mr Wong yesterday took over the investigation into a bomb hoax on March 12. On that occasion a box left outside the Legislative Council carried slogans attacking Mr Wong and Chief Executive-designate Tung Chee-hwa. Tsim Sha Tsui police are investigating a hoax bomb protesting against property prices, left on Tuesday on a bus outside Star House. A police spokesman said there was no plan to offer Mr Wong special protection, but added: 'The police take a very serious view of recent cases of criminal intimidation . . . police officers will spare no effort in investigating these cases and arresting the culprits.' A police source said: 'While we would not rule out the possibility of the threats coming from the same person, they could be copycat cases.'