A construction worker found a mummified body in the wall of the Oakland convention center on Wednesday, authorities said.

The body was found during renovations at the Henry J. Kaiser Convention Center, the Alameda County Sheriff’s Office said.

The partially decomposed corpse probably had been there for several years and had mummified, authorities said.

The decomposition made it impossible to immediately determine the age or gender of the body, the Sheriff’s Office said.

The city-owned convention center near Lake Merritt has been closed since 2005. But in 2015 the City Council reached an agreement with a developer to lease the building and turn it into a commercial and performing arts space.