As a federal review begins, a new chapter has been added to the marathon Michigan state scrutiny of the contested $500-million tunnel plan for the Straits of Mackinac crossing by Enbridge Inc.’s Line 5.

Enbridge Line 5

“The record in this case is reopened to receive testimony, exhibits, and rebuttal,” the Michigan Public Service Commission (MPSC) said in a 51-page order for details of safety measures in the current underwater pipeline and the proposed buried route.

MPSC’s order is the latest in a longstanding legal battle between Enbridge and the state.

According to MPSC, the order requires “documents and any other relevant information to develop a full and complete record on matters including tunnel engineering and safety, electrical equipment and risk of fire and/or explosion,...