Noida, Sep 20 (PTI) A portion of a housing society"s boundary wall collapsed here on Tuesday morning, killing four people and injuring eight, police said. All 12 who had been buried under the rubble at Jal Vayu Vihar in Sector 21 around 10 am were labourers. Multiple JCBs were deployed to clear the debris of the collapsed stretch of wall that was located adjacent to a drain, officials said as police and fire department personnel swing into action for immediate rescue and relief measures.        "A total of 12 labourers were pulled out of the rubble. Four of them died while others suffered injuries in the episode," Additional Deputy Commissioner of Police (Noida) Ashutosh Dwivedi told PTI.         Police Commissioner Alok Singh, Joint Commissioner Love Kumar and Noida Authority CEO Ritu Maheshwari were among those who reached the spot.        Fire Service officials, including its chief Arun Kumar Singh, were also there to oversee relief measures officials said. PTI KIS  MIN MIN