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

That finding opens a window onto a little-remembered period in which blacks 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, said district officials and court records.

This week, archaeologists announced that the bones were most likely those of 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.

About half of the bodies have been exhumed, and more than 20 have been analyzed. Of those analyzed, archaeologists said, all but one were male, ranging in age from about 14 to 70. All were black, and some may have been former slaves.

It is rare to discover a black cemetery from this time period, but rarer still to find a grave site of black prisoners from the convict lease era, said Ken Brown, a professor at the University of Houston who specializes in African-American archaeology.

“You have a chance to study what the actual bone material has to say about what life was like — … we know it was tough — but what impact does all of that have on the body?” he said.

Researchers hope to run tests that could tell which diseases the prisoners lived with, what kind of foods they ate and where they grew up. “It really does change the history books in Texas,” said Reign Clark, a lead archaeologist on site.

The 13th Amendment to the Constitution abolished slavery in 1865, except as punishment for a crime. Several Southern states, including Texas, used this exception to outsource prisoners for labor, Brown said.

It was “more or less slavery by a new name,” said Reginald Moore, a historian and prison reform advocate. He noted that vagrancy laws at the time made it so that blacks were often convicted of minor offenses, such as loitering, and sentenced to years of hard labor in the fields.

From 1870 to 1912, 60 percent of prisoners in Texas were black, said the Texas State Historical Association. During this time, prisoners helped build the Capitol building in Austin and constructed part of the Texas State Railroad.

So far, the results show that the men who were buried there lived difficult lives, researchers said. Their bones show stress from poor health during childhood, such as fever and malnutrition, and stress from repetitive work later in life.

Moore, who has been fighting for recognition for black convict laborers, said he hoped the findings would encourage Texas to remember them and include their stories in history books and memorials. He said, “When I went out there and seen those bodies, I felt so elated that they would finally get their justice.”