The authorities directed a probe into the small plane crash, wherein the plane sunk into Lake Michigan on Friday morning. The investigators are searching for the four people who went missing after the crash.

The plane was headed for Mayo Clinic, taking a cancer affected patient to the health centre. The team looked for the four missing people however, they could not find anyone.

Brandon Blackwell, Officer at U. S. Coast Guard's district headquarters in Cleveland, said that the team tried to enquire if any of the missing people were alive. But, the search could not determine anything.

"We can resume a search if credible information is received that persons missing may be alive. At this point, we saturated an area that's approximately 1,000 square miles", he said.

Those who went missing include Dr. James Hall, co-pilot Earl Davidson, Alma schools Superintendent Don Pavlik and his wife Irene.

It has been confirmed that the pilot has survived. The missing individuals are all residents of Alma.

The plane was carrying Pavlik to the clinic for further treatment, as he got diagnosed with cancer the preceding week. Freed and Davidson volunteered to accompany him.