Rescue operation continued today at Paarichcha thermal power station near here amidst apprehension that some labourers are still being trapped under the debris of a chimney, which collapsed leaving six labourers injured, officials said.

"No casualty has been reported so far and efforts are on to clear the debris after which the clear picture would emerge," Senior SP Vinod Kumar Dohre said.

While there were apprehension that several labourers were still trapped under the debris, the SSP said the exact number could be ascertained only after the debris was removed.

Though heavy machines including JCBs and cranes have been pressed into service, only 20 per cent debris could be removed till morning, officials said.

Six labourers were injured when an approximately 220 metre high under-construction chimney collapsed yesterday at the power station, some 30 km from the district headquarters.

The army was also called to assist in rescue work.

The chimney, which was being constructed by National Building Construction Corporation, collapsed during lunch time while the labourers were taking rest, officials said.

Power department sources claimed there were inputs suggesting that the chimney was slightly titled towards a side and directives had been issued to rectify it.

"As the structure of the chimney was made from iron, gas cutters were being used, besides machines of different agencies including NHAI and BHEL to remove the debris," an official spokesman said in Lucknow.

Chief Minister Mayawati alleged that the quality of work done by the executing agency, a central government undertaking, was of low standard and had directed the officers to write to the Centre recommending action against NBCC.