A village in Yuen Long was in mourning yesterday for two boys killed in a fire at their home.
Investigators were checking a burned-out air conditioner for faulty wiring.
Eight-year-old Elliot Watkiss and his brother Frankie, seven, were asleep in the first-floor bedroom of the family's house in Pat Heung Upper Village when the fire broke out shortly before 1am.
The boys' parents, British actor Simon Watkiss and his Hong Kong wife Candy, a schoolteacher, were said by friends to be distraught.
The boys were rushed to Pok Oi Hospital but were declared dead on arrival.
It is believed they may have died from smoke inhalation.
The family's Indonesian helper, 35, who shared a room with the boys, was found unconscious and was in a critical condition at North District Hospital last night.
Relatives and friends visited the Watkiss home yesterday to pray and burn paper offerings.
Mr Lai, a farmer in his 60s, said he saw the two boys less than a week ago and was in shock.
He said: "Just last Sunday, they came here to play in the water and catch small fish. I knew them since they were small so it really pains my heart. My whole family loved the two boys."
The two families were very close because the Watkiss' domestic helper started taking the boys when they were just babies to the Lai family home, a three-minute walk away, to play with Lai's daughters.
A long-time resident in her 50s said the two young boys always greeted her. She said: "I felt so sad when I heard about it."
A woman in her 70s wept as she spoke of the boys. "They were so polite, well-behaved and handsome. Every time they walked past me with their mother, she would tell them to say hello to me," she said.
The entrance to the Kam Wing Garden complex of about eight village homes was cordoned off by police tape as investigators and staff from CLP Power examined the Watkiss' home.
Their efforts focused on an air conditioner and they used equipment understood to be used to test for faulty wiring.
The boys' parents returned to the family home briefly yesterday afternoon.
Their father Simon appeared in a recent TVB commercial for baby milk powder.
Their mother Candy is a teacher at the WF Joseph Lee Primary School in Tin Shui Wai, where the boys went to school.
Yuen Long police are investigating the fire, which is not thought to be suspicious.