India, Dec. 21 -- The Delhi government on Saturday threatened severe action against those violating curbs under the Stage-4 of the Graded Response Action Plan (Grap) to curb pollution, as Delhi once again was in the grip of "severe" air quality.

The air quality index (AQI) was 398 ("very poor") at 4pm, according to the Central Pollution Control Board's (CPCB's) daily bulletin. By 6pm, it deteriorated to 405 ("severe") by 6pm and 409 by 8pm.

Delhi's environment minister Manjinder Singh Sirsa said, "Grap Stage-4 continues to be in place but there have been complaints of construction work being carried on in several parts of Delhi."

He said that strict action will be taken against those who are not complying with curbs under Stage 4 of Gr...