A teacher took her own life a day after it was alleged that she had an inappropriate physical relationship with a young student.

Gretchen Krohnfeldt had been suspended from her job at the school in Denver, Colorado.

The following day, the 47-year-old mother of three took her own life in front of police officers who were approaching her home to question her as part of an investigation, CBS News reports.

Ms Krohnfeldt was reportedly suspended after a fellow member of staff reported witnessing an “inappropriate interaction” between her and a former student at the Drake Middle School.

Police were informed and launched an immediate and ongoing investigation.

"On Monday, May 8th, a Jefferson County Sheriff’s Office School Resource Officer was made aware of a possible inappropriate relationship between a female employee at Drake Middle School and a male student," Arvada police said in a statement.

A spokesman added that the boy is now attending an Arvada high school, but had been in a physical relationship with the teacher since middle school.

Local media report the pair had met at Ms Krohnfeldt's home, and that an employee saw an inappropriate interaction between Ms Krohnfeldt and the student months ago but only reported it to authorities earlier this week.

Students who attend middle school in the United States are usually between the ages of 12 and 14.

Ms Krohnfeldt's death is being investigated by a coroner.

In a letter to parents and students, Drake Middle School said grief counsellors were available to see both students and staff upset by Ms Krohnfeldt's death.

"Our hearts go out to her family at this painful time," the letter said, "and I know many will feel this loss deeply," it said.