The Customs Department has opened investigation papers on traders not complying with the Goods and Services Tax (GST), said its director-general Datuk Seri Khazali Ahmad.

He said the papers were opened since the GST came into force on April 1 to find out the number of cases that could be brought to court.

"After two weeks, that is on April 15, we will know better the status on compliance to GST," he told reporters after launching a national-level operation to weed out outlets selling contraband cigarettes and alcoholic drinks here on Thursday.

He said sale of contraband alcoholic drinks was causing the government to lose RM500 million in revenue yearly.