The 37-year-old defenceman played for the New York Islanders last season and was suspended hours before their playoff loss to Buffalo on April 20. He received a 20-game suspension and will miss the first 19 games of this season.
The Wild said Hill acknowledged using a doctor-prescribed testosterone booster approved by the NHL, but tested positive for the anabolic steroid boldenone, which is banned.
Hill told the team he did not knowingly take boldenone and is unsure how it got in his system.
"We have talked to Sean at length, and he denies knowingly taking any banned performance-enhancing substance," the Wild said in a statement. "We also researched the situation and the substance Sean tested positive for and found that boldenone can be ingested inadvertently through health supplements and foods. We cannot determine the source of Sean's test failure. However, we believe Sean did not knowingly take any banned performance-enhancing substance."
At the time of Hill's suspension, Islanders GM Garth Snow said the team supported the league's decision, saying the "New York Islanders do not support the use of performance-enhancing agents in any form."
Under the new collective bargaining agreement, a player receives a 20-game suspension for a first positive test and is subject to a mandatory referral to the league's substance abuse-behavioural health program for evaluation, education and possible treatment.
Every NHL player can be given up to two tests without notice every year, at any time.
Hill had one goal and 24 assists in 81 games for the Islanders last season. The hard-nosed native of Duluth ranked third in the NHL in hits and sixth in blocked shots.
Islanders goalie Rick DiPietro called Hill "one of our most consistent defencemen all season, and an unbelievable character guy."
An eighth-round pick of Montreal in the 1988 draft, Hill has also played for Anaheim, Ottawa, Carolina, St. Louis and Florida.