Detectives are investigating reports that a flammable liquid was poured through the letterbox of the home in Whitburn, West Lothian, before the blaze was started.
A man and woman in their 40s were forced to flee from the Townhead Gardens flat through a window shortly before the arrival of firefighters, who were called to the property at around 10.40pm on Sunday.
Fire investigation teams said yesterday that sniffer dogs had picked up evidence of an accelerant at the scene, indicating the blaze had been started deliberately.
Detectives have appealed for those with information to come forward as it emerged fire crews were called to the same address in October to put out a fire that was later investigated by police.
One neighbour said: “I just heard the brakes of the fire engine outside the house and there were blue flashing lights coming through my bedroom window.
“When I got up the dogs barked.
There was shouting on the street – but it could have been them coming out of the house. It could have been anything.
“The police are never away from that house. It hasn’t even been a year since the last fire.”
Another neighbour said: “When I came out of my bedroom, there was smoke billowing out of the window of their flat.
“They had to break down the door to get in.
“After the fire last year, the council came in and did it all back up and for them to go back in and have that happen, it’s shocking.”
Trevor Lynch, a crew manager and dog handler with Central Scotland Fire and Rescue, said: “Lothian and Borders Fire and Rescue asked us for assistance and requested we bring in our fire investigation dogs to look for the possibility that accelerants were used.
“The dogs have detected something suspicious.”
A spokesman for Lothian and Borders Police said yesterday: “Thankfully no-one was injured during this incident.
“However, the reckless conduct of whoever was responsible could have put all residents in the stairwell in serious danger.
“Anyone who remembers seeing anything suspicious in the Townhead Gardens area last night, or who has any other information that can assist with our investigation is asked to contact police immediately.”
Police have appealed for any witnesses who think they may have information to call them on 0131-311 3131.
Thug breaks man’s jaw
AN Italian man was left needing surgery to a broken jaw after being punched in an unprovoked attack in Leith.
The 30-year-old had been standing with his 29-year-old Spanish friend outside Pearce’s Bar in Elm Row at 11pm on Saturday.
A gang of around ten men and women approached the pair and one of the gang punched the victim, who fell to the ground.
Appealing for witnesses, police said the area was busy following the Scottish Cup final, but said they did not believe the attack was football-related.