The parents of two Chinese graduates murdered in Newcastle have appealed for help in finding the killers. The bloodstained bodies of Zhen Xing Yang and his girlfriend Xi Zhou, both 25, were found in separate rooms of the ground floor flat on Croydon Road on August 9. The couple's pet cat was also drowned by their killers. Police believe Mr Yang, known as Kevin, was tortured for up to an hour before he was hacked and stabbed to death by his killers, who then turned on Wagamama noodle bar waitress Xi Zhou, who was known as CiCi. Mr Yang's mother Shu Zhen Qu, 52, a hairdresser from Dalian City in northeast China, wept as she begged anyone with information to contact police, saying: "We felt as if our hearts had been broken when we lost him in this terrible way. "While we are here, we ask people with a kind heart to provide information to the police so that they can arrest the murderer as soon as possible. It will reassure all the parents who have children studying abroad." She said the family had spent their life savings to send Kevin to study in England, adding: "My son never caused any trouble. He was a kind and forgiving person. He loved his parents so much." Xi Zhou's father Sanbao Zhou, 58, said: "When we were informed of the death of our daughter we almost lost the will to live. However, we cannot do that as the murderer of our daughter is still at large. "I am determined to catch the murderer. I have no doubt the murderer will be arrested and my daughter will have the justice she deserves." The parents attended a joint funeral service, conducted by a Chinese pastor and translated into Mandarin, at Sunderland Crematorium on Wednesday. Detective Superintendent Steve Wade of Northumbria Police said detectives still need to trace a lodger who had arranged to sublet a room in the couple's flat from August 1 and could hold vital clues to the murders. He said the most likely motive for the killings was a robbery or burglary, as detectives recovered no cash from the flat and several personal items were stolen. He confirmed the students had been part of an internet gambling scam using mobile telephones to forward results from football matches throughout the UK. Police believe the scheme would not have made the couple much money, but that their involvement in it could have led others to believe they did.