Authorities deployed the Rapid Action Force and the Provincial Armed Constabulary to ease tension in Allahabad which witnessed violent protests.
"The General Studies (Paper I) has been cancelled," a senior UP government official told media after an emergency meeting convened by Chief Minister Akhilesh Yadav to take stock of the situation.
The meeting was attended by Chief Secretary Alok Ranjan, DG Police A K Jain and some other senior officers, besides UPPSC Chairman Anil Yadav, who was summoned from Allahabad, the headquarters of the Commission.
The decision to cancel the first paper was taken after it leaked on Whatsapp messaging service just before the examination was to commence at 9.30 AM yesterday, leaving lakhs of aspirants high and dry.

As the news of the paper leak spread, the DGP immediately handed over the probe to STF, which swung into action and arrested three persons.
A senior STF official told media on Monday that the paper was leaked from Adarsh Bharti Vidyalaya College centre here allegedly by Vishal Mehta, Gyanendra and Jay Singh - all of whom have been arrested.
The three allegedly took photographs of the question paper an hour before the examination and it was circulated on Whatsapp.
Vishal is the son of Baldev Mehta, Manager of ABV College, which was made PCS exam centre for the first time. "Our college was made PCS examination centre for the first time and the examination was overseen by my son Vishal," Baldev said.
About the two others -- Gyanendra and Jay Singh – arrested by the STF, he said they were invigilators and were on contract.
"The two had earlier also performed duties as invigilators in other examinations," Baldev said, feigning ignorance about the leak.
Around 4.5 lakh candidates had appeared in 917 centres across the state, including 70,000 candidates in Lucknow who took the test in 148 centres.

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