Ten other workers who were trapped survived the Saturday accident, the Nigerian Tribune reported. Two were in critical condition, the newspaper said.
A witness said the building's decking collapsed "suddenly" about 10:45 a.m., about 45 minutes after a crew of 25 workers had started taking the building apart.
The building was owned by Alhaji Suleiman Danzaria, who bought it from St. Faith Catholic Church, which had ceased using it two years ago, the newspaper said. Danzaria had contracted to have it torn down, the newspaper said.