Over 45% votes were cast in Sunday's by-poll to the Howrah Lok Sabha seat in West Bengal till 2pm.
Joint chief election officer Saibal Barman said the polling was peaceful so far with no incident reported from any assembly segment.
A few EVMs went out of order or malfunctioned at the beginning of the polls and were replaced promptly, he said.
The Election Commission is for the first time using GIS-SMS based poll monitoring system, android-based counting application and live monitoring of sensitive areas (LMSA).
The GIS-based poll monitoring system is being used in rural areas to capture images and LMSA for Howrah city, with a video camera on a vehicle being used for the first time.
All polling stations are being monitored by digital cameras and video cameras and by micro observers. High resolution digital cameras have been installed in all the 1851 booths, EC sources said.
Tight security is in place with central forces and state armed police deployed.
"All booths are covered by an armed guard," chief electoral officer Sunil Gupta said adding that general observers Vijay Bahadur Singh and I Anwarudeen, besides an expenditure observer Ranjit Kumar are monitoring the bypoll.
Polling began at 7am and will end at 6pm, two hours more than the normal schedule.
The election has been necessitated by the death of Trinamool Congress MP Ambika Banerjee.
The main fight is between Trinamool Congress, Congress and CPI-M. TMC has fielded former India football captain Prasun Banerjee, while the Congress nominee is lawyer Sanatan and that of CPI(M) is Sridip Bhattacherjee, a former party district secretary.
Though BJP is not contesting the by-poll, local BJP leader Ranjan Pal is in the fray as an independent.