The comedian's whereabouts and condition have been unknown since Comedy Central abruptly announced last week that the planned May 31 launch of the third season of "Chappelle's Show" had been postponed and production halted.
Chappelle flew from Newark, New Jersey, to South Africa on April 28 for treatment, said the magazine, quoting a source close to the show it would not identify. Entertainment Weekly said it had corroborating sources for its story.
"We don't know where he is," Comedy Central spokesman Tony Fox said. "We've heard about South Africa. We don't know. We haven't talked to Dave."
Chappelle's spokesman, Matt Labov, would not comment on the magazine's story.
"It seems like the issues he's contending with are really quite serious," said Dade Hayes, a senior editor at Entertainment Weekly. "It isn't a case of him spending a weekend someplace recuperating from exhaustion."
The magazine's sources say Chappelle is still in the facility, which was not named, Hayes said. Chappelle's representatives have denied that the comedian was abusing drugs.