In this phase, a total of 1,35,72,339 voters will elect MLAs to 49 Assembly seats for which 583 candidates, including 54 women, are in the fray.
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The polling will be held between 7 a.m and 3 p.m in nine constituencies - Tarapur, Jamalpur, Suryagraha, Rajauli (SC), Govindpur, Sikandara (SC), Jamui, Jhajha and Chakai.
In four constituencies - Alauli (SC), Beldaur, Katoria (ST), Belhar - voting will end at 4 p.m.
The polling for the remaining 36 constituencies will be held between 7 a.m and 5 p.m.
The duration of polling hours in 13 Assembly seats have been shortened on the basis of assessment of law and order situation with all these constituencies falling in Naxal-hit areas, Additional Chief Electoral Officer (ACEO) R Laxmanan said.
Of the total electors, there are 72,37,253 male, 63,17,602 female and 405 third gender, he said.
Among the break-up of seats being contested by different political parties in the first phase, the BSP leads the pack with 41 candidates, followed by BJP (27), RJD (17), LJP (13), Congress (8) and RLSP (6).
Among the left front constituents, the CPI has fielded 25 candidates followed by the CPI-M at 12.
As many as 13,212 polling stations have been set up for the first phase for which 63,624 polling personnel have been deployed, he said.
Laxmanan said that 1.20 lakh personnel of Central Paramilitary Forces have been deployed to ensure free and fair polls adding that every polling station will be manned by a CPF personnel.
Out of the total number of 13,212 polling stations, 7,384 are tagged as critical and 2,255 are Left-Wing Extremists-hit.
He said that five helicopters, including three Unmanned Aerial Vehicles (UAVs) have been deployed for air surveillance during polling.
The number of mounted police force to be used for patrolling stands at 50, while 33 motor boats have been pressed into service for riverine petrolling.
As many as 935 video cameras and 339 android mobile phones have been put into use to ensure free and fair poll, the ACEO said.