Cannabis investor MMJ Group has begun its first proper day of trading after a six-week holiday from the bourse, with shares in the company falling 21 per cent the moment the market opened.

MMJ Group (ASX:MMJ) owns minority stakes in 10 businesses, and has been in trading suspension since October 5 as it transitioned from medical cannabis company MMJ Phytotech to cannabis investment company MMJ Group.

MMJ shares fell from its October 4 close of 33c to 26c when the market opened this morning.

Yesterday, the company’s shares accidentally spent a couple of hours trading thanks to an ASX error; they dropped 30 per cent to 23c, but the trades were cancelled and the order book purged.

MMJ Group had told investors on Tuesday that it would recommence trading on Thursday, November 22.

The ASX released a note saying MMJ’s shares were “reinstated to the official quotation today in error”.

An ASX spokesman told Stockhead this morning that “it was an ASX Operations error. The stock was reinstated to trading 24 hours before it should have been”.