Volkswagen Chief Executive Matthias Mueller has cast doubt on a report which last week said many managers at the German carmaker knew of, or were involved in, developing emissions test-rigging devices.

Volkswagen’s (VW) development of software to cheat diesel-emissions tests was an open secret in its engine development department, Germany’s Sueddeutsche Zeitung reported on Jan. 22, citing results from VW’s internal probe.

The newspaper, which researched the matter with regional broadcasters NDR and WDR, cited a whistleblower which they said was himself involved in the deception and had testified to investigators hired by VW.

“No one has spoken with me,” Mueller told reporters on Thursday at a reception of auto executives. “You got the information from some sources who have no idea about the whole matter.”

Mueller also damped expectations VW could release the first public results of an investigation into the scandal by U.S. law firm Jones Day before its shareholders’ annual general meeting (AGM) on April 21.

Top players on the German manufacturer’s supervisory board will hold their third meeting in three weeks on Wednesday as they continue to grapple with the scandal more than four months after it broke, sources have said.

“Is it really so difficult to accept that we are obliged by stock market law to submit a report to the AGM on April 21 and that it is not possible for us to say anything beforehand?”, the CEO asked.