The two horses in question can't be identified until further testing takes place but they won't be Smith's two group one winners, In Her Time and El Dorado Dreaming, because all swabs taken from the autumn carnival were negative.
"He has been suspended indefinitely until the charges are determined," Van Gestel said.
"He can continue to train for seven days then won't be able to train any further but he
can't start a horse in a race from this day forward."
Stewards found the unidentified substances in Smith's stables, vehicle and house and his mobile phone and computer were confiscated for forensic imaging.
Stewards decided to suspend Smith because he posed an "unacceptable risk to the image, interests and integrity of racing".
It's too soon to say if Smith's horses will be transferred to other stables.
But In Her Time can only have her scheduled track gallop in between races at Newcastle on Friday if she is transferred to another stable or Smith appeals and he's allowed to run her in his name. The track gallop was always seen as a crucial part to In Her Time's Everest preparations and she's an $11 chance to win the A$13 million race on October 13 at Randwick.
"It's an environment that places stress on people," Van Gestel said.
"He still has a right of appeal and that will be there first thing he needs to look at, and if he doesn't, they'll need to look at transferring his horses."