The opening bowling pair were withdrawn from the biennial one-day tournament after internal tests were conducted by the PCB before the players left for India.
"They have tested positive for using nandrolone, which is a performance enhancing anabolic steroid," Saleem Altaf, director of cricket operations of the PCB, told Reuters on Monday.
"We have asked for a second test (B sample). But for the moment they have been suspended and are being recalled from India," he added.
Nasim Ashraf, new PCB chairman, will make a formal announcement at 1000 GMT following an urgent board meeting.
"What was my initial reaction? Disappointment," Pakistan coach Bob Woolmer told a press conference in Jaipur.
"We asked the (PCB) medical panel to give the players drug tests which they did at the end of September, so I take responsibility for that certainly," added the English-born coach.
"I have never come across anything like this in my life. The timing is not great, but if it's going to happen it happens."
Replacement pacemen Mohammad Sami and Shahid Nazir, along with all-rounder Yasir Arafat are being prepared to fly out to India as soon as possible a PCB official told AFP on condition of anonymity.
Months of trouble
Pakistan cricket has been embroiled in controversy since August 20, when the fourth Test against England at the Oval was awarded to the hosts amidst allegations of ball tampering and Pakistan captain Inzamam ul-Haq bringing the game into disrepute.
Fast bowler Mohammed Asif also
failed a PCB drugs test
Since then Pakistan have been found not guilty of altering the state of the ball, but Inzamam was banned for four one-day internationals for bringing the game into disrepute, thus ruling him out of the Champions Trophy.
Shaharyar Khan, former PCB chairman, then resigned from his position after Younis Khan initially declined to captain the team for the Champions Trophy in Inzamam's absence, before agreeing to take the post two days later.
There have also been threats of protests against the Pakistan team by right-wing Hindu political party Shiv Sena, who believe the neighbouring team should not be allowed into India due to terrorism fears.
Pakistan are scheduled to commence their Champions Trophy campaign on Tuesday against qualifiers Sri Lanka in Jaipur.