A fire near an overpass in downtown Fresno led crews to a grim discovery of two bodies in an underground vault. 

It happened Monday morning when firefighters were called to the area just before 8:30 a.m. for reports of smoke rising from a utility vault beneath a bridge overpass near H and Fresno streets, the Fresno Fire Department said in a Facebook post. A video posted by the department shows a massive plume of smoke billowing several feet off the side of the road.

Construction workers reportedly told officials they saw two unhoused individuals enter the vault earlier that day, the department said. The department called the operation “unique and hazardous,” requiring multiple teams, including a search and rescue team and a hazardous materials crew.

Before fire crews could enter the vault, PG&E had to cut power to the surrounding area because it serves as a major electrical distribution circuit for downtown. Once the power was shut off, fire crews accessed a hatch, extinguished the fire and eventually found two people inside.

Both people were pronounced dead at the scene, the fire department said.

Fire crews and law enforcement are investigating the cause of the of fire and working on identifying the two people.

Fresno Fire Department Chief Billy Alcorn told the Fresno Bee that some unhoused individuals may have been living in the underground area, which is about 40 feet below the overpass.

The Fresno Fire Department did not respond to SFGATE’s additional questions in time for publication.