22-year-old defender Stochl and versatile forward Fantis, 17, have also attracted interest from Italy and Pribram chairman Jaroslav Starka is not surprised Celtic are stepping up their pursuit.
"Such an interest, not only of Celtic of course, is a big evaluation of the work in our club," Starka told iDnes.cz.
"For instance, Fantis was trialled by Celtic a year ago. They were speaking of him highly but he was only 16 back then so it was better for him to go back to the Czech Republic and continue his career there.
"That is why we set up another trial for him. Moreover, they want to have a look at one of the most talented Czech stoppers, Jakub Stochl."
Ondrej Chovanec, the agent for both players, has warned Celtic to expect competition from elsewhere for their signatures.
"Pribram are developing some very talented footballers," said Chovanec.
"For instance, Stochl is being tracked also by Catania while Fantis was tested by Juventus at the start of November."