Four men who tried to kidnap billionaire Florence Tsang Chiu-wing's mother and four-year-old daughter last week left no fingerprints or images that investigators could trace, according to police.
Investigators are working with 'very limited information', and 'blurry' pictures of the assailants from security cameras at the crime scene make it difficult to ascertain their identities, one officer says.
No arrests had been made as of yesterday and police said the victims did not know the perpetrators.
The suspects had forced the girl and her 60-year-old grandmother inside the elderly woman's chauffeured car outside the ESF International Kindergarten (Hillside) on Stubbs Road, Wan Chai, last Wednesday afternoon.
They dragged the chauffeur out of the seven-seater Toyota after threatening him with what appeared to be a pistol. The perpetrators, thought to be aged between 20 and 40, gagged the grandmother's mouth with tape and tried to drive away with the car.
However, the culprits were unable to start the vehicle because the gear stick was not in 'park' position.
An expatriate man shouted at them, prompting the gang to flee on foot. An air pistol, a paper cutter and adhesive tape were found at the scene. No one was injured.
Officers believe that since the men were not wearing gloves and there were no fingerprints at the crime scene, the suspects had wrapped their fingers with tape.
'They also wore either caps or masks to hide their identities from surveillance cameras or passers-by,' a senior police officer said.
The officer said it was possible that the driver had panicked and put the gear lever in the wrong position or did not know how to start a car with automatic transmission.
The four men may have had lookouts around the scene, police say. Detectives from Hong Kong Island regional crime unit are investigating all possibilities.
'We are keeping an open mind,' another officer said. The girl's family did not receive any threat or warning before the incident, he added.
Police have stepped up patrols around the victims' home and the school.
Tsang became Hong Kong's newest billionaire after being awarded a divorce settlement of HK$1.2 billion in December from real-estate scion Samathur Li Kin-kan.