A construction crew renovating a historic former convention center in California made a grim discovery this week of a mummified human body behind the walls, authorities said.

Workers were tearing down a wall inside the Henry J. Kaiser Convention Center in Oakland Wednesday afternoon when authorities got a call about “what appeared to be a body, a human form, in the wall,” Alameda County Sheriff Lt. Ray Kelly told HuffPost.

The body, upon closer inspection, was determined to be “somewhat preserved” after spending “several years to maybe longer” encased in the walls, said Kelly.

Though it’s age is not immediately known, the body is believed to be that of an adult male, Kim Armstead, a public information officer with the Oakland Police Department, told HuffPost.

“We’re hoping we can rehydrate the fingers using our medical technology and hopefully get some fingerprints and any type of DNA,” Kelly said of current efforts to identify the remains.

It is unclear how the body got there.

“I think we can speculate anything from, they were placed in there or they fell or got in behind the wall, they were seeking shelter. It’s hard to say,” he said, adding that there were no obvious signs of foul play. “It’s not a common occurrence for something like this to happen but it has happened before.”

The building, which is a locally registered historic landmark, was ordered closed in 2005 after serving more than 90 years as a concert hall, theater, sports arena and briefly a hospital during the 1918 flu pandemic. Its closure followed the city determining that its operating costs were unsustainable, according to the city’s website.

In 2015, Oakland’s city council greenlighted a private company’s proposal to turn the building into a performing arts venue and commercial space. Construction on the building was slated to begin in 2020, CBS San Francisco reported.

Kelly said this week’s discovery is being treated as a missing person case with the help of local forensic anthropologists.

“It’s a missing person, obviously, someone we didn’t know about so that’s an angle we need to explore. Is this a person we’ve been looking for, a family’s been looking for?” he asked.