Investigators are trying to determine the cause of a train derailment Thursday night in Wausau.

The last three cars of a Canadian National freight train jumped the tracks and one of them crashed into an office building in the rail yard. A cleaning worker inside was not hurt, but the crash damaged the walls and heating system.

Rail spokesman Patrick Waldron says the cause and circumstances of the crash remain under investigation.

Crews spent the morning Friday working to get the cars back on track and remove them.

Matt Lehman, WSAU

Oshkosh police Chief Scott Gruele (Photo: Mike Kemmeter)

Police says the body of a man found in the Fox River Monday was the son of an assistant coach for the Green Bay Packers. Oshkosh Police Chief Scott Greuel says they have identified the man as 21-year-old Michael Philbin, son of Packers offensive coordinator Joe Philbin.

Police are working to retrace the young man’s footsteps before he disappeared Sunday morning. Philbin, a student at Ripon College, was meeting friends at the UW-Oshkosh on Saturday night. Greuel says he became separated from them at some point in the evening, with a “non-distress” call made from his cell phone at around 2:10 Sunday morning.

AUDIO: Andrew Beckett reports (1:00)

Police then received a 911 call at around 2:30 am Sunday from a security guard at a business along the Fox River. The caller reported hearing someone crying for help and then seeing a person’s head above the surface of the river.

Philbin was reported missing later in the day on Sunday.

Greuel says foul play is not suspected. Police are still trying to determine if alcohol was a factor and an autopsy is being conducted to determine the cause of death.

WHBY’s Mike Kemmeter contributed to this report.

The state Emergency Operations Center Madison is elevated in response to an incident at a nuclear power plant on the Mississippi River. There’s been no release of any radiation at the Prairie Island Nuclear Power Plant near Red Wing, Minnesota. Lori Getter with Wisconsin Emergency Management says they responded to an alert early Thursday from the plant operated by Minnesota-based Xcel Energies. There was a leak of sodium hypochlorite, commonly known as chlorine bleach, which is used to help cool water. The leak was found near a tank and has been contained by crews. It’s not known how the leak started. Getter says there was no release of chemical fumes, and cleanup got underway at about 7:30 Thursday morning.