MINNEAPOLIS (WCCO) – St. Paul police say a registered sex offender was taken into custody last week after he was discovered sitting on a school bus returning from a field trip.

According to an incident report, officers responded to Chelsea Heights Elementary School just after 1 p.m. on Feb. 28 for a report of an unauthorized man on a school bus. Police arrested 61-year-old Michael Charles Friedrichs for sex offender registration violation.

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His previous crimes include engaging in sexual activity with two 15-year-old boys, as well as exposing himself to other children.

(credit: Minnesota Department Of Corrections)

The bus driver immediately called police when Friedrichs was discovered sitting in the back of the bus, according to a statement from St. Paul Public Schools.

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Police say Friedrichs told officers he had been at the Walker Art Center and had boarded the wrong bus.

St. Paul Public Schools district is conducting its own investigation “to learn more about what happened and to strengthen our bus safety procedures. SPPS has also informed its school bus contractors about the incident to reinforce our required safety protocols,” according to a statement.

Chelsea Heights Elementary School is in regular communication with families and students affected by the situation, SPPS said.

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Friedrichs was booked into the Ramsey County jail, but he has been released since no charges have been filed against him.