Dreze, who was a member of the National Advisory Council headed by Sonia Gandhi during the erstwhile United Progressive Alliance regime, and Vivek Gupta, an activist, were eventually released, they added.
"Dreze and Gupta were taken into preventive custody for organising a programme without taking permission which violated model code of conduct in operation now," Bishanpura police station in-charge Vijay Kumar Singh said.
They were set free after an investigation, he said.
Dreze is a specialist in Development Economics and had helped draft the food law.
Congress president Rahul Gandhi expressed concern over Dreze's detention, alleging that the Bharatiya Janata Party was in a 'state of war' with everybody who works for the poor and the downtrodden.
'I am extremely concerned about Mr Dreze's detention. The BJP is in a state of war with everybody who works for the poor & the downtrodden,' Gandhi said in a Facebook post.
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