An elderly man found lying on the MRT tracks between Tanah Merah and Expo stations on Saturday is in a stable condition.
Mr Koh Chai Seng, 75, was still in an intensive care ward at Changi General Hospital yesterday afternoon, but awake and able to converse with family members.
What remains a mystery is how he ended up on the tracks.
Mr Koh was unable to explain it, but police are reviewing close-circuit television footage and collating eyewitness accounts to determine how it happened.
His son Steven Koh, 47, said his father had fractured some ribs and hurt his left leg, and was due for surgery today.
He insisted it was "impossible" for his father, who did not even own an ez-link card, to scale the 1.5m-high platform doors. He said his father has shown symptoms of dementia for the past decade, and also suffers from epilepsy.
"He goes out alone every day, but doesn't say where he goes, and he doesn't know either. But he could always find his way back home," said Mr Steven Koh, who lives with his parents, younger sister, wife and two primary school children.
He said his father would sometimes be gone for a day or two, and on occasion, be escorted home by the police or taxi drivers.
But on Saturday it was different - he received a call from the hospital at about 4pm. According to him, his father had breakfast before leaving their four-room flat in Bedok at about 9am on Friday.
He was spotted on the elevated tracks close to the Expo station by the driver of an approaching train at about 1.40pm the next day.
SMRT said the driver "immediately applied the emergency brake and stopped the train".
The police and SMRT declined to reveal more information on how the elderly man ended up on the tracks, as investigations are still ongoing.