TRACY, Calif. -- A missing teenager ran into a fitness center Monday with an inch-thick chain shackled to his ankle, and he may have been held captive, Tracy police said.

Wearing just boxer briefs, the 17-year-old burst into an InShape Fitness Center at about 4 p.m., said Chuck Ellis, who works at the gym.

Michael Schumacher, 34, and Kelly Lau Schumacher, 30, are being questioned after being apprehended at a Tracy home where the boy was allegedly held, police spokesman Matt Robinson said.

No charges have currently been filed against the married couple, police said.

Ellis said the boy looked emaciated, bruised, scared and said, "Hide me, please hide me."

"He was hunkered down, terrified," Ellis said.

The teen told gym employees that he was taken from a group home about a year ago, Ellis said. The group home is about 70 miles north of Tracy, in Sacramento.

Robinson said the boy was confused when first approached by detectives, unsure where he had come from and how long he was being held against his will.

"The wounds he had and his physical condition as well as having a chain around his leg corroborated his basic statement that he was being held against his will," Robinson said.

Covered in dirt or soot, the teen was also bleeding on his back and had a significant cut on his arm, Ellis said.

Robinson said detectives planned to interview the boy, who was taken to Sutter Tracy Community Hospital, more extensively Tuesday when he is a "little healthier."

The boy is currently in serious but stable condition.