TORONTO — The Toronto Blue Jays say they are conducting an internal investigation after six players in the team's minor-league system were suspended for using performance-enhancing substances over the past week.

Major League Baseball suspended five minor-league players on Tuesday, including three in Toronto's system, for violations of the Minor League Drug Prevention and Treatment Program. That announcement came four days after three Blue Jays were caught up in another round of MLB suspensions.

"This situation is very disappointing and disturbing to the organization; disappointing that the players made these choices, but more so disturbing that some failure of our environment allowed this to happen," Blue Jays general manager Ross Atkins said in a statement Thursday. "It is our responsibility to create an environment and culture where our players know that PED use is not condoned, and to give them resources and education to ensure that they do not make these decisions.

"As we seek to determine both how and why this happened, an internal investigation into the situation remains ongoing, and we will double down on ensuring that all our staff is properly equipped to help our players make the right choices."

Right-handed pitcher Juan Jimenez, left-handed pitcher Naswell Paulino, shortstop Hugo Cardona, infielder Yhon Perez and catcher Leonicio Ventura — all of the rookie-level Dominican Summer League Blue Jays — each received a 72-game suspension without pay.

Right-handed pitcher Jol Concepcion of the rookie-level Gulf Coast League Blue Jays was handed a 60-game suspension. All six tested positive for the performance-enhancing drug boldenone.