GRAND RAPIDS, Mich. (WOWO)  — Federal authorities are investigating after a U.S. Postal Service employee died Saturday at the Detroit Network Distribution Center in Allen Park.

The maintenance worker, in his 30s, was reportedly trapped inside a mail-handling machine for several hours according to WDIV. His fiancée alerted authorities when he failed to return home, and investigators determined he had been deceased for six to eight hours before being found.

Mail-handling machines, used to sort and weigh mail, range in size from compact units to large industrial equipment. The Allen Park facility contains many large machines.

Authorities have labeled the death an accident. The Michigan Occupational Safety and Health Administration has not yet released information, and federal officials will lead the investigation due to the incident occurring in a federal building.

The USPS expressed condolences to the family and confirmed the distribution center remains fully operational.

“The United States Postal Service is deeply saddened by the loss of our employee at the Detroit Network Distribution Center in Allen Park. Our thoughts and prayers are with his family,” the agency said.