The tilting of a Yokohama condominium blamed on faulty piling work for its foundation has shaken public trust in housing safety in this quake-prone country. Revelations that several workers at a subsidiary of Asahi Kasei Corp. — in addition to the one in charge of the work at the Yokohama condo — were falsifying data on piling work at possibly hundreds of buildings across Japan over the past decade have stirred up suspicions that such practices are widespread in the construction industry. The companies involved must reveal as quickly as possible the whole picture of the wrongdoings and find out whether and how they affect the safety of the buildings in question. The industry and relevant authorities also need to get to the bottom of why these problems are allowed to happen.

Residents of the Yokohama condominium complex, which was completed in 2007, noticed last year that handrails in one of the buildings connected through passageways with those of the adjacent building had sunk about 2 cm — an indication that something was amiss. Asahi Kasei Construction Materials Corp., a subcontractor in charge of the work to drive piles into the ground to provide underground support for the buildings, admitted last month that data on the work on dozens of such piles had been manipulated and that eight of the piles supporting the tilting structure had either not reached the solid ground called the support layer or were not driven into it deeply enough.

The data falsification was initially blamed on one employee responsible for the work at the Yokohama complex, who was also found to have been involved in piling work at 43 other buildings over the past decade. Asahi Kasei Construction Materials and its parent company later revealed that piling work data had been falsified in 19 buildings. The companies also confirmed that more workers were similarly falsifying data on piling work for other projects. Although they have not disclosed the number of workers and the buildings in question, media reports suggest that at least 10 employees had fabricated such data in about 10 percent of the roughly 3,000 construction sites where the Asahi Kasei subsidiary was in charge of piling work over the last 10 years, ranging from condominiums and factories to school buildings, medical facilities and hotels.