The bodies of the children were found on the Mumbai-Nashik Highway in Kasara on Tuesday morning.
Shah, who had slit his wrists to commit suicide, was under treatment and was discharged on Saturday.
Shah was found unconscious by the police in the same region where the children’s bodies were found.
He was taken to Thane Civil Hospital and later shifted to KEM Hospital ICU.
He was discharged from the hospital on Saturday evening and later arrested by the police. Shah had gone missing since Sunday when he stepped out telling wife Swati he was taking the kids to his father’s house in Panvel.
He was found unconscious in the same jungle where bodies of the children were found.
Police will now interrogate Shah to learn details of his movements from the time he had left his residence with Janhvi and Parag till the day he was found unconscious in the forest near Kasara Ghat.
Police said Shah had already confessed to having strangled his children.
After killing them, he roamed in the area for a day before returning to the spot where he had left the bodies.
On seeing them gone, he went into the forest and slit his wrists, said police.
Meanwhile, police have placed Shah under strict watch to prevent him from attempting suicide again.
“He was already depressed over his wife’s mental instability, and now says he will have to live with his children’s blood on his hands. Officers are watching him round the clock. Care is being taken to ensure he does not get his hands on any sharp object or any poison,” said an officer with Kasara police.
Inquiries conducted so far indicate that the murders were premeditated. Shah had removed the SIM card from his cell phone and left it home before leaving.
Police said that after strangulating his children, he placed his ATM card in the pocket of Janhvi’s jeans, which helped the cops to identify her.
Nitin Shah left home on Sunday, telling wife Swati he was taking the children to his father’s place
He took the children to Kasara where he strangulated them.
He then slit his wrist, and was found near the spot where the children’s bodies were discovered
Nitin told police he had planned to commit suicide, but killed the children as he was worried about their future