General Motors Co. warned its engineers against using the words "safety" and "defect" when identifying product risks, and explicitly told them not to use inflammatory terms including "widow-maker" and "Hindenburg," according to company documents released by the U.S. government on Friday.

U.S. officials, in announcing a $35 million fine against GM for its delayed response to a deadly ignition switch flaw in certain vehicles, say the documents show a dangerous company culture.

The confidential GM training documents, which were used during a 2008 technical learning symposium, give engineers replacement words. The company advised them to use "does not perform to design" instead of "defect," and "condition" instead of "problem."

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David Friedman, the acting head of the National Highway Traffic Safety Administration, said the materials robbed the company of essential terms needed for engineers and investigators to clearly flag problems to higher-ups.

"GM must rethink the corporate philosophy reflected in the documents we reviewed," Friedman said.

The Detroit automaker is facing multiple investigations into why it took more than a decade to respond to evidence of a deadly ignition switch flaw that has been linked to at least 13 deaths. It has recalled 2.6 million vehicles due to the risk that the cars can unexpectedly stall, disabling air bags, power steering and power brakes.

A spokesman for GM, Greg Martin, said the company's culture has changed since the 2008 training session and cited a program the company has put in place to encourage candid conversation about safety issues among GM engineers.

"Today's GM encourages employees to discuss safety issues, which is reinforced through GM's recently announced Speak Up for Safety Program," Martin said in a statement.

The 2008 documents released on Friday show a GM highly sensitive to how engineers' testing reports could make their way outside the company. One slide referenced "the brutal facts" that recalls and NHTSA investigations were grabbing headlines each week.

"For anything you say or do, ask yourself how you would react if it was reported in a major newspaper or on television," the documents said.

In a particularly colorful section, the slides sternly warned engineers against embellishment and "judgment words."

One slide includes dozens of words or phrases that should be avoided, including: "asphyxiating," "deathtrap," "disemboweling," "genocide," "grenadelike," "Hindenburg," "powder keg," "rolling sarcophagus," "Titanic," and "you're toast."

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