TOKYO, June 3 (Reuters) - Toyota Motor said on Monday its chairman would address an investigation by Japan's transport ministry into the company's auto certification applications.

Chairman Akio Toyoda will hold a news conference at 0800 GMT on Monday, the company said.

The transport ministry said separately it will conduct an on-site inspection at Toyota's headquarters on Tuesday after saying irregularities were found in model applications from Toyota, Mazda Motor, Yamaha Motor, Honda Motor and Suzuki Motor. (Reporting by Rocky Swift; Editing by Kim Coghill)