The oil-slicked man was found after a resident heard a "faint voice" coming from a vacant Chinese food restaurant in San Lorenzo and called authorities, police said. Responders found the man wedged in a sheet metal grease duct that ran from the roof to the kitchen.
The man couldn't move, and it took firefighters an hour to free him, according to the sheriff's department. He was "physically exhausted and suffering from dehydration" and taken to the hospital, the department said. He's expected to make a full recovery.
The Alameda Sheriff's Department has opened a trespassing and vandalism investigation and is looking into whether the man, who has not been identified, was trying to commit a burglary.
Elisha Fieldstadt is a breaking news reporter for NBC News.