Tokyo CNN  —  Japanese officials descended on the headquarters of Toyota on Tuesday, after a safety test scandal at a number of automakers in the country widened this week. The inspections at Toyota’s offices in central Japan would continue over the next few days, Japan’s Ministry of Transport told CNN. It comes as the world’s biggest carmaker by sales grapples with growing concerns over the certification of some of its vehicles. The ministry said five automakers — Toyota (TM), Mazda, Honda (HMC), Suzuki and Yamaha — had submitted incorrect or manipulated safety test data when they applied for certification of the vehicles. Toyota, Mazda and Yamaha were ordered to suspend shipments of some vehicle models, including the Corolla Fielder and Corolla Axio. All five companies were told to review their safety certification processes. A probe already undertaken by Toyota had revealed that at least seven of its models, some of them discontinued, were tested using methods that differed from government standards, the company said Monday in a statement. Toyota was looking into “inadequate data in pedestrian and occupant protection tests” and “errors in crash tests,” it said. The investigation is ongoing. Toyota said it had not violated safety regulations and customers did not need to stop using their cars. Toyota's headquarters are in central Japan. Kyodo/Reuters Koji Endo of SBI Securities said that Japan’s certification tests are very stringent and much stricter than in other countries. “As for these safety inspection standards, this rule was created in 1951, so it’s quite outdated and hard to follow for many automakers,” he said. “We have to remember, Toyota has conducted hundreds of thousands, if not millions of tests throughout the past 15 years. And of those tests, there were only concerns about how three or four of those tests were conducted. That’s very little,” Endo added. Photo taken from a Kyodo News helicopter on Dec. 25, 2023, shows a Daihatsu Motor Co. factory in Oyamazaki in Kyoto Prefecture, western Japan. The small-car unit of Toyota Motor Corp. said the same day it will suspend production at all domestic factories until at least the end of January due to a safety testing scandal. (Photo by Kyodo News via Getty Images) Kyodo News/Getty Images Related article Toyota-owned automaker halts Japan production after admitting it tampered with safety tests for 30 years Still, because of its position as the world’s top carmaker, the scandal had become “a big problem” for the company, he said. In a press conference Monday, Akio Toyoda, the grandson of Toyota’s founder and company chairman, apologized for the problems. “I intend to extend our efforts throughout the entire group and restore authority on site to create a solid corporate culture that makes ever-better cars,” he said. Operations at Toyota’s factories will not be halted during the probe but production will pause for the three models under investigation, the Transport Ministry said. It said officials would also inspect the facilities of the other four carmakers but did not say when those visits would take place. In January, Toyota announced it would suspend shipments of certain models after finding irregularities in certification tests for diesel engines developed by its affiliate, Toyota Industries. The revelations came just a month after Daihatsu, the Japanese small carmaker owned by Toyota, halted domestic production after admitting it had forged the results of safety tests for more than 30 years.