"The labourers were rummaging through the waste which was to be transported when the blast occurred," Deputy Inspector General of Police PK Ramashastri told PTI.
While three persons died on the spot, two were critically injured, he said. Senior UP police officials, including Ramashastri, have rushed to the spot.
The injured were admitted to a nearby hospital where their condition was stated to be critical. "It appears to be an accidental blast," Ramashastri said.