St. Paul police are asking for the public's help in finding a vulnerable 17-year-old boy who they say left home Tuesday morning in a "manic state."

Joseph C. Kaiser, who is 6 feet 2 and 200 pounds, rode off on a one-pedal bike, police spokesman Peter Panos said Wednesday.

He is considered vulnerable because he has bipolar disorder, police say.

There is no indication of foul play, Panos said.

When last seen, Kaiser was wearing a light gray sweatshirt, bluejeans and a black backpack.

He lives in the 2100 block of St. Clair Avenue.

Anyone with information is asked to call the department's missing-persons unit at 651-266-5646 or 651-291-1111.