POLICE in Central are looking for a man who is believed to have defrauded horse owners and racing personalities of more than $500,000 in the past six months. Five complaints have been lodged. The victims reportedly told police that they had received a telephone call at home from a man using the name of a horse trainer or jockey who needed cash urgently. The victims then deposited up to $100,000 at a time into the man's personal bank account as instructed. Police said the suspect went into hiding after withdrawing all the money from his account. Raids at several addresses failed to find him. ''We are investigating how the culprit had access to information about the horse owners such as their home telephone numbers,'' said a spokesman. ''There's no indication to suggest the man is an employee or ex-staff member of the Royal Hongkong Jockey Club. ''We think we know who the man is and we hope to make an arrest when he surfaces.'' The victims denied the caller offered any favours in return. ''I think the victims were a bit stupid to think the man was the person they knew without finding out his true identity or opting to meet face-to-face,'' a police source said. The head of the security department of the Jockey Club, George Redfern, said yesterday it was aware of the recent incidents. ''We have had talks with the racing department and a circular has gone to all owners alerting them and advising them to be particularly vigilant,'' he said . ''This is not the first time that this has happened.''