NEW YORK, Oct 22 (Reuters) - U.S. federal prosecutors are trying to determine whether Japanese auto parts maker Takata Corp misled U.S. regulators about the number of defective air bags it sold to automakers, including Toyota Motor Corp and Honda Motor Co Ltd, The Wall Street Journal reported on Wednesday.

Word of the investigation follows a notice on Tuesday from the U.S. auto regulator, the National Highway Traffic Safety Administration, which increased the number of cars potentially affected by defective air bags made by Takata to at least 7.8 million, up from the roughly 4.74 million it announced a day earlier.

The NHTSA is conducting its own investigation of whether Takata air bag inflators made between 2000 and 2007 were improperly sealed. Bags inflating with too much force potentially could spray metal shrapnel at occupants. They have been linked to four deaths and resulted in several lawsuits.

The probe has focused on inflators recovered from cars being recalled for repairs in hot and humid regions such as Florida. Takata is cooperating with that investigation along with 10 automakers.

The NHTSA has urged owners of certain Toyota, Honda, Mazda Motor Corp, BMW AG, Nissan Motor Co Ltd , Mitsubishi Motors Corp, Subaru Co Ltd , Chrysler , Ford Motor Co and General Motors Co vehicles to replace air bags as soon as possible.

More than 16 million vehicles globally have been recalled since 2008 because of defective Takata air bags.

Reuters previously reported that manufacturing problems with Takata's air bags go beyond what the Tokyo-based company disclosed to the NHTSA about why the devices were at risk of exploding with dangerous force, citing internal company documents.

According to Wednesday's article in The Wall Street Journal, the investigation by the U.S. attorney's office for the Southern District of New York is in very early stages. The company has not been accused of any wrongdoing.

A spokeswoman from the U.S. attorney's office in Manhattan declined to comment.

A spokesman for Honda said the company was not aware of the investigation.

Spokespeople for Takata and Ford could not immediately be reached for comment.

A BMW spokesman declined to comment on the possibility, adding that the German automaker is focused on carrying out the recall as fast as possible.

Spokespeople for Toyota and Chrysler said they had no information on a possible federal investigation of Takata.

Spokesmen for Mazda and Mitsubishi said their companies had not been contacted by the U.S. Department of Justice and could not confirm the report.

A Nissan spokesman said the automaker had no knowledge of such an investigation and declined further comment.

Spokespeople from Subaru and GM declined to comment. (Reporting by Emily Flitter; Additional reporting by Ben Kalyman; Editing by Andre Grenon, Sandra Maler and Leslie Adler)