The skeletal remains of three women found in or near a Washington, D.C. apartment building under construction were of homicide victims, police said.

Police and a medical examiner said two of the victims “suffered from gunshots” and the other “suffered from trauma,” FOX 5 DC reported.

Investigators were attempting to gather DNA from family members of missing people to confirm a match with the victims. Investigators are also looking into whether the three women's deaths were associated.

The FBI has joined in the investigation, The Washington Post reported.

SKELETAL REMAINS OF THREE WOMEN FOUND NEAR WASHINGTON, D.C. APARTMENT BUILDING

Some pieces of clothing were found at the scene, investigators said. So far, none of the victims have been identified, but the process could take months.

Authorities believed the victims’ bodies have been in the shallow grave for at least a year.

The remains were found on April 25 after workers were digging underneath the first floor of an apartment building in Congress Heights. The crew enlarged a crawl space to construct more apartments and found the bones, which included a skull and jawbone. The workers believed they were animal remains at first until they saw the skull.

“But when he saw the skull and the jaw, he figured it was a person,” Adan Escobar, one of the construction workers, said according to The Washington Post.

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After police were notified, investigators searched the rest of the building and a nearby wooded area. Cadaver dogs found two additional sets of remains – both female – last Saturday in a shallow grave.

Police announced that they are offering a $25,000 reward to anyone who comes forward with information leading to an arrest in connection with the homicides.

Fox News' Lucia Suarez Sang contributed to this report.