The remains of dozens of people found at a construction site in Texas this year are most likely those of African-Americans who were forced to work on a plantation there around the turn of the 20th century, officials said this week.

That finding, announced Monday, opens a window onto a little-remembered period in which black people in certain Southern states were essentially treated like slaves post-emancipation.

The remains of about 95 people were discovered early this year on a construction site outside Houston, where the Fort Bend Independent School District is building a new school, according to school district officials and court records.

This week, archaeologists announced that the bones were most likely those of African-American laborers who worked as part of the so-called convict lease system, in which the state of Texas outsourced prisoners to work and live on plantations. The researchers estimated that the cemetery, which was on the plantation’s grounds, was used from 1878 to 1911.