A special investigation group in the Mexican state of Sonora uncovered a mass grave Thursday near the resort town of Puerto Penasco, just south of the Arizona border.

The Madres Buscadoras de Sonora – translated as “Searching Mothers of Sonora” – is devoted to finding such burial sites in the interest of helping the families of missing people. The group is composed of such family members.

“I take comfort in knowing that families are going to be united with their loved one...and that they will have a proper burial, like they deserve,” group founder Ceci Patricia Flores said in a statement to Tucson ABC affiliate KGUN9.

At least 42 bodies have been found at the site. The initial discovery consistent of 12 complete skeletons and a partially decomposed body near the Gulf of California. On Friday, a further 15 bodies were found, the Arizona Republic reports.

While it is unknown exactly how long ago the bodies were buried, the state of decomposition on some of them indicates that it was somewhat recently. Most of the remains found have been skeletal. The genders and identities of the deceased are difficult to discern at this point, but two are assumed to have been female based on clothing.

The reason for the mass burial is also unknown at this time and is currently under investigation.

Puerto Penasco is more than 200 miles south of Phoenix.

Missing case
A bag to collect forensic evidence is seen as the New York City Office of Chief Medical Examiner hosting DNA Extraction demonstration to unveil groundbreaking technology in New York, on Sept. 6, 2018. Getty Images/ANGELA WEISS