National Australia Bank's BNZ subsidiary has put New Zealand's third largest commercial construction company Mainzeal into receivership.Receiver Colin McCloy, from PricewaterhouseCoopers, has not disclosed the size of Mainzeal's debts to BNZ. Mainzeal has been a major player in New Zealand's commercial construction sector and is working on dozens of projects, including a joint venture with Suncorp Metway's New Zealand insurers Vero and AA Insurance to manage the earthquake rebuilding of 7800 commercial and residential claims in Christchurch.Prime Minister John Key said he expected Mainzeal would be liquidated and competitors would buy the various parts of the business completing projects in Christchurch and elsewhere. Mainzeal has 400 staff and hundreds of sub-contractors.The sole remaining director of Mainzeal, Richard Yan, called in the receivers after the company's parent, Richina, failed to provide support for the business. This followed a series of losses on leaky buildings in Auckland and problems paying for supplies from a Chinese building materials supplier. The receivership has shocked the industry, given the recent upswing in activity linked to the Christchurch rebuild. Meanwhile, NAB reported BNZ's cash earnings rose in the December quarter because of lending growth and higher fee income. It said loan quality was stable.