TOKYO, June 4 Reuters Japanese transport ministry officials launched an onsite investigation at Toyota Motor39;s headquarters on Tuesday after irregularities were found in its applications to certify certain vehicle models.

The widening fallout over certification tests stems from a safety test scandal at Toyota39;s Daihatsu compact car unit and has also ensnared other Japanese automakers after the ministry ordered industrywide checks of certification practices.

Toyota, Mazda, Honda, Suzuki and Yamaha Motor they had submitted either flawed or manipulated data when applying for certification of vehicles.

Toyota, Japan39;s largest automaker, was the first to undergo an inspection which was flagged by the ministry on Monday. The other four automakers will also be inspected, a ministry official said.

While some analysts noted that Toyota will be under more pressure to strengthen governance, others said the impact on sales is likely to be limited given that it is only suspending sales of three models and so many of its domestic rivals also fell short of ministry standards.

When it comes to actual sales in the Japan market, the damage will be manageable or quite small, because consumers basically have no alternatives in Japan, said James Hong, head of mobility research at Macquarie.

Hong added that Toyota Chairman Akio Toyoda is likely to come under more pressure. Proxy advisory firms Institutional Shareholder Services and Glass Lewis have recommended shareholders vote…