Hong Kong's shares prolonged downward trend on Friday weighed down by energy firms as US oil futures and metal prices tumbled. Asian investors remained cautious ahead of upcoming US nonfarm payroll report. Hang Seng index dropped 0.78% or 164.79 points and settled at 21,084.74 with technology sector fading most. Cnooc Ltd sank 1.3% and PetroChina Co fell 1.6%. Aluminium Corp. of China Ltd lost 2.7%. Export oriented clothing retailer Esprit Holdings gave up 5.5%.