Superintendent of Police Manoj Kumar Jha said that raids were conducted last night but there was no clue about Singh's whereabouts.
There were unconfirmed reports that Singh could surrender in the court in Lucknow.
The SP said that Singh's brother Dharmendra was detained for questioning, but failed to give any information.
"All he said was that Singh left for Gorakhpur on July 21 and there was no contact since then," he said.
Jha said that police raided the house of Singh's uncle at Bariya last night, but nothing was found.
"His mobile is switched off since July 20 night," he said.
Singh had sparked an outrage by his derogatory comments questioning the character of the BSP supremo. He had said that "Mayawati is breaking the dream of Kanshi Ram into pieces. Mayawati is selling tickets like a...
BSP workers held a protest against the derogatory remarks made by Singh. BSP workers, who staged a dharna in front of the Bhimrao Ambedkar statue in Hazratganj, had displayed banners with foul language printed on them yesterday.
Meanwhile, Singh's family today lodged an FIR against Mayawati, saying it was question about the integrity of women. The case was registered against Mayawati, BSP general secretary Nasimuddin and and two others.
"My husband is in politics, but we have no political connection. The manner in which BSP workers acted yesterday and the language used by them during protest was derogatory," Swati, wife of Singh, said.
Swati said that her family was being dragged into the controversy unnecessarily.
"Why Mayawati is not taking action against Nassemuddin Siddiqui. Why he was not expelled from the party. I don't want to imagine what is the state of my 80-year-old mother-in-law," she said.
"While BSP leader Satish Chandra Mishra said that nothing like this happened, but the entire country has witnessed and listened the foul language used by BSP workers during protest yesterday. It is about the integrity of women," she said.