Mike Garafolo of NFL Network shared an Instagram story posted by Edelman, who said he isn't sure what triggered the positive PED test result:
The 32-year-old Kent State product missed the 2017 season after suffering a torn ACL during the team's third exhibition contest.
On Tuesday, he talked about getting the chance to participate in practice again after the Pats kicked off their mandatory offseason minicamp.
"Any time you get to go out and see the fellas, play with them, talk with them, be in the huddle and look at guys, and participate in drills, that’s what you play the game for ultimately," Edelman told reporters. "It was tough to watch it on the sidelines last year. To come out here and do little things, strap on the helmet, it put some perspective on how lucky you are to get to play the game."
The California native has made 425 career catches since New England selected him in the seventh round of the 2009 draft. He tallied 98 receptions for 1,106 yards and three touchdowns in 2016.
Edelman is one of the Patriots to highlight his work with Alex Guerrero, the trainer of quarterback Tom Brady. In December, Bob Hohler of the Boston Globe reported Patriots head coach Bill Belichick "stripped Guerrero of his special team privileges," including treating players other than Brady at Gillette Stadium.
The Patriots released a statement from Guerrero, who denied any connection to the suspension after it was first reported Thursday.
"Here at our facility, we take a natural, holistic, appropriate and, above all, legal approach to training and recovery for all of our clients," he said. "And anyone who would suggest otherwise is irresponsible, and just plain wrong."
If the four-game ban is upheld, Edelman would be eligible to return for a Week 5 clash with the Indianapolis Colts after missing games against the Houston Texans, Jacksonville Jaguars, Detroit Lions and Miami Dolphins.