Pandey's body was found on the tracks about one km from the Ghaziabad railway station late last night and a suicide note was also recovered from the spot, they said.
Bihar Chief Minister Nitish Kumar condoled the death of the officer. "He was a capable administrator and a sensitive officer. May god bless his soul," he said in a tweet.
In the purported note, Pandey, a 2012-batch IAS officer, said he was fed up with his life and has lost his "faith in human existence".
Officials of the Government Railway Police (GRP), who reached the spot, near Kotgaon here, said prime facie it was a case of suicide.
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Police said Pandey's post-mortem was conducted today by a team of three doctors in Ghaziabad and it was videographed.
The body will be transported to Guwahati where his family lives and the last rites will be conducted there, they said.
Before taking the extreme step, Pandey had sent messages to his family members that he was planning to commit suicide at Janakpuri District Centre.
A senior Delhi Police official said that police received information from his friends that Pandey would commit suicide and had gone to the Janakpuri District Centre yesterday.
The police received information around 6.30 pm and started analysing the CCTV footage but it was seen that he had left the mall around 6 pm.
The police carried out searches in nearby malls, hotels and even shut down some shops and the entrance to the top floors to scan the corridors but he could not be traced.
Later, the Delhi Police learnt that he had allegedly committed suicide, the official said.
Around 8.10 pm, the Sarojini Nagar police station in south district was informed by Pandey's sister-in-law that he was missing.
The Delhi Police said they are awaiting a report from their counterpart in Ghaziabad before taking future course of action.