FRANKFURT, Germany (AP) — Volkswagen's diesel scandal took a rancorous turn Wednesday when the board of directors denied news reports that former chairman Ferdinand Piech had given four members early warning about the U.S. probe into emissions cheating.

The board issued a statement that the four members "rejected all assertions made by Ferdinand Piech as untrue."

The reports from the Bild newspaper and Spiegel Online say Piech has told German prosecutors that he learned of the probe from an informant and asked CEO Martin Winterkorn about it in March, 2015, then told the four.

Winterkorn has said he didn't learn of the problem until shortly before U.S. investigators announced it in September, 2015. Investors are suing in Germany, saying Volkswagen didn't give timely notice of an issue that could affect share prices.