"Anna Hazare was detained because he said he intended to defy prohibitory orders," Home Secretary R K Singh told reporters here.
The Home Secretary was responding to questions on why 73-year-old Hazare was taken into custody by the Delhi Police.
Official sources said the Home Ministry has sought a report from the Delhi Police on the circumstances leading to the detention of Hazare, his other associates and overall situation in the national capital.
The report is expected later in the day, sources said.
In an early morning crackdown, Hazare and his close aides were detained by police after the Gandhian vowed to go ahead with his fast for a strong Lokpal and defy prohibitory orders at the venue of his agitation.