WMFS said in a statement: “The cause of the fire was accidental and involved a pedal bike that had been converted into an electric bike, which was stored in the hallway of the property.
“No further information relating to the cause or the victims who sadly lost their lives in this tragic accident will be released at this time.
“Our thoughts remain with everyone affected by this tragic accident.”
Four fire crews were sent to the scene, the first arriving within four minutes.
Crews wore breathing apparatus to enter the property and extinguished the blaze by 05:55 GMT.
An investigation was carried out by fire investigations officers and a fire investigations dog, together with police.
