Two crude bombs exploded in the head office of the State Revenue Board in Lucknow on Thursday afternoon, officials informed.
No casualties were reported and the police said crude bombs were used to set off the explosion.
"The explosion took place in the dustbin of the general bathroom and initial investigation has revealed that two crude bombs were used," Lucknow police chief Akhil Kumar told IANS.
The entire office has been cordoned off and a rigorous search is being conducted to find any other such explosives, he added.
Similar crude bomb explosions took place consecutively on Nov 14 and 15 in the bathrooms of the Lucknow district court, followed by yet another explosion in the Sultanpur district court.
"Like previous incidents, this also appears to be the handiwork of mischievous elements and we will soon nab them," additional director general of police (Crime, law and order) Brijlal told IANS.