More than 120 missing children have been found safe during a one-day sweep in Michigan.

Authorities located the children in the Wayne County area, which includes Detroit, as part of the one-day operation last month — a first of its kind in the county.

According to a report released by the U.S. Marshals Service, out of 301 files of missing children, 123 were identified and recovered safely during the operation which took place on September 26.

The U.S. Marshals Service said Operation MISafeKid placed an emphasis on locating missing children who were victims of sex trafficking.

"All of the children were interviewed and potentially victimised or used in a sex trafficking ring during their period of time they that they were deemed missing," the statement read.

Authorities discovered three cases that were related to sex trafficking and one homeless teen who had not eaten anything in three days. The teen was transported back to the command and turned over to Child Protective Services for after-care.

The operation involved multiple law enforcement agencies, including the U.S. Marshals Service's Detroit Missing Child Recovery Unit, Michigan State Police and Wayne County officers.

The U.S. Marshals Service said they had been requested to assist on 30 missing child cases in the two weeks prior to the sweep.

They visited last known addresses, friend's homes and schools in the hope of finding the children in a safe place.

Officers in the operation also obtained information about two missing children in Texas and another in Minnesota. Those cases are being actively investigated, officials said.

"The message to the missing children and their families that we wish to convey is that we will never stop looking for you," the US Marshals Service said in its report.

The U.S. Marshals Service also said Michigan State Police have asked for assistance with 14 other cases.

"The Eastern District of Michigan is fully committed to assisting state and local agencies with locating and recovering missing children and the prevention of their falling victim to sex trafficking," the U.S. Marshals Service said.