The skeletal remains of three women found near a construction site in Washington, DC were homicide victims, according to police.

The bodies are still unidentified, but the medical examiner has determined that two were killed by gunshots and the third died from trauma. It is believed that the women 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,” Fox News reports.

After the first body was found, cadaver dogs were used to search the area and two more were discovered.

The FBI has now joined the investigation to help determine the identities of the women. A forensic anthropologist will be using DNA to determine the ancestry of the women and hopefully figure out their names.

DC Police Chief Peter Newsham told the Washington Post that they have not yet determined if the killings are related.

The DC Police have announced a $25,000 reward for information leading to an arrest.