(Reuters) - An internal NBC News probe has determined a “seasoned” producer was to blame for a misleading clip of a 911 call that the network broadcast during its coverage of the Trayvon Martin shooting, according to two sources at the network.

A woman holds an image of black teenager Trayvon Martin while taking part in a rally demanding justice for his killing in Miami, Florida April 1, 2012. REUTERS/Lucas Jackson

NBC News brass interviewed more than half a dozen staffers during its investigation of the misleadingly edited 911 call placed by George Zimmerman just before he shot the unarmed Florida teenager, said the sources, one of whom is an executive at the network.

The clip aired on the network’s flagship “Today” morning show last week.

The edit made it appear that Zimmerman immediately told police that Martin was black, when, in fact, the full tape reveals that the neighborhood watch captain only did so when responding to a question posed by a dispatcher.

There was no clear indication on Thursday of what, if any, disciplinary actions would be taken against the producer or other staff involved in the incident.

The sources at the network, who declined to identify the producer, said NBC News executives did not know the 911 call was misleadingly edited until news reports surfaced days later on right-leaning blogs including Newsbusters.org and Breitbart.com.

“IN SHOCK”

The sources described the producer’s actions as a very bad mistake, but not deliberate.

NBC News declined to comment on Thursday. The network said on Tuesday it would not release names of the employees involved. It has apologized for the incident.

One of the sources said that NBC News President Steve Capus would not lose his job over the incident.

The Today show’s editorial control policies - which include a script editor, senior producer oversight, and in most cases legal and standards department reviews of material to be broadcast - missed the selective editing of the call, said the NBC executive.

Executives have vowed to take rigorous steps to formalize editorial safeguards in the news division following the incident, one of the sources said.

NBC News staffers who have been working on the Trayvon Martin story for several weeks in Florida were at first “in shock” over the incident, and later furious, another source, who is an NBC producer, told Reuters.

Public pressure has been building on the network to fully explain the incident - which critics charge has inflamed racial tensions in an already volatile situation.

On Thursday, a New York Post editorial characterized the edited 911 call as “pretty damning evidence of willful misconduct by NBC News” and suggested that racial violence could ensue over irresponsible news coverage.

Television news veterans in New York said they were baffled over how the error came to be broadcast given the intense vetting such a sensitive story would normally get at a major network such as NBC.

Executives from parent company Comcast Corp, including Chief Executive Brian Roberts and Chief Operating Officer Steve Burke, who doubles as the CEO of NBC Universal, are not involved in the investigation, two sources inside the network said.

NBC’s Today - which has dominated the U.S. morning landscape for more than a decade - is currently in a ratings war with ABC’s Good Morning America, which has been picking up viewers.