The Federal Aviation Administration has received at least four calls from potential Boeing employee whistleblowers about issues with the company's new 737 Max jetliner, CBS News has confirmed.

The calls began coming in within hours of Ethiopian investigators releasing a preliminary report on the second of those crashes, that of Ethiopian Airlines Flight 302 last month.

A source familiar with them confirms the April 5 calls were from current and former Boeing employees alleging possible issues related to the angle of attack (AOA) sensor and the MCAS anti-stall system that relies on data from the sensor.

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Both have been linked to the two deadly 737Max crashes that killed nearly 350 people and lead to the grounding of the aircraft worldwide.

One of the claims deals with damage to the wiring of an AOA sensor from a foreign object.

Boeing said it could not verify the report but in a statement tolds CBS News, "Safety and quality are absolutely at the core of Boeing's values. Speaking up is a cornerstone of that safety culture and we look into all issues that are raised."

A Boeing source was skeptical of that particular whistleblower allegation, saying that as far as he knows, there have been "no reported issues...at all" with foreign object debris damage to AOA sensors or their wiring.

But, as CBS News confirmed last week, Boeing has had issues with foreign object debris (FOD) being found in the company's 787 Dreamliner assembled at its South Carolina plant, including metal shavings discovered by the FAA in aircraft Boeing certified as debris-free as recently as 2017.

Twice this year, the U.S. Air Force stopped accepting delivery of the 767-based KC-46 aerial refueler because FOD was found inside the newly delivered aircraft. The KC-46 is built in Everett, Washington.

Another of the potential whistleblower calls dealt with concerns over the shutoff switches for MCAS.

The four calls were made to call came in through a special hotline setup by the FAA for employees or the public to report problems. They are being evaluated by FAA investigators as part of ongoing probes into the 737 Max and its certification.

If true, it's possible the allegations could lead to additional investigations.

The hotline submissions were first reported by CNN and confirmed to CBS News.

Earlier this month, the Senate Commerce Committee launched an investigation into the FAA certification process, citing whistleblower claims of improperly trained FAA inspectors working on the Max.

House Transportation and Infastructure Committee investigators have reportedly been speaking with potential whistleblowers. The committee has not responded to a CBS News request for comment.

It's unclear if any of these whistleblowers overlap.

Boeing's CEO was expected to attend the company's annual shareholder meeting Monday and participate in his first media availability since the crash of Ethiopian Airlines crash. He was expected to take reporters' questions.