Chinese car maker BYD, backed by US billionaire Warren Buffett, said Wednesday that its first-quarter net profit shrank 84 percent because of increased costs and falling auto sales. The firm earned $266.7 million yuan ($41.2 million) in the three months ended March 31, well below its $1.7 billion yuan net profit in the same quarter last year. The Hong Kong-listed company also said its operating revenue fell almost 12 percent to $11.7 billion yuan in the quarter, down from $13.25 billion a year ago. \"This was mainly due to a decline in automobile sales performance coupled with an increase in management and finance expenses,\" BYD said in a statement. The firm\'s A-shares will make their trading debut in the southern Chinese boomtown of Shenzhen on Thursday after BYD raised a lower-than-expected $1.4 billion yuan in a share sale earlier this month. BYD\'s latest results come as China\'s auto sector which overtook the United States in 2009 to become the world\'s largest car market has lost steam after the government phased out most sales incentives implemented to ward off the worldwide economic downturn. Sales fell 3.98 percent from a year earlier to 1.38 million units in May, declining for the second straight month. BYD\'s Hong Kong shares were 5.2 percent lower at HK$23.75 ($3.05) in morning trade Wednesday.