Three persons were killed and two injured on Saturday in an explosion in an army waste dump in Ahmednagar area of Merut.
"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.

Similar blast in Ahamedabad. To destroy communal harmony.

At least two people were killed as seven synchronised blasts hit India's western Ahmedabad city on Saturday, police said.
Forty-eight people were injured in the explosions that occurred in busy areas in Ahmedabad, among the top commercial cities in India, the NDTV network reported.
Police officials told the news channel that the blasts occurred within 15 minutes starting at 6.45 pm (1315 GMT) local time in the eastern areas of Sarkhej, Maninagar, Sarangpur, Isanpur, Diamond Market, Bapu Nagar and Narol Circle.
The bombs appear to have been planted on bicycles or in tiffin boxes in Ahmedabad, some 50 kilometres south-west of Gandhinagar, the state capital of Gujarat state.
No militant group claimed responsibility for the attacks.
Indian President Pratibha Patil condemned the blasts and asked people to maintain peace and communal harmony.
Police expressed fear the bombings could trigger sectarian clashes in Gujarat, which has witnessed large-scale riots between Hindu and Muslims in the past.
Additional police forces were dispatched to the sensitive areas to maintain law and order.
The blasts come a day after eight low-intensity bombs shook the southern city of Bangalore, claiming two lives.