In the middle of an investigation into why General Motors allowed vehicles with defective ignition switches to not only hit the market, but continue to be sold and driven for years while at least 13 people died, the carmaker has placed to engineers directly involved with this issue on paid leave.

Bloomberg reports that one man led the engineering team on the Chevrolet Cobalt, the vehicle most associated with this recall. Documents turned up during the Congressional investigation into the recall indicate that this engineer rejected a potential fix to the ignition issue, saying it would take too long and cost too much money.

The other engineer led the team that designed the faulty switch in the recalled vehicles. He later, and apparently without the knowledge of others at GM, gave the third-party part supplier the green light to produce improved switches in 2006. However, the part number was not changed, so people who repaired these vehicles may have later replaced a perfectly good part with a defective one since there was no way of knowing which was which.

“This is an interim step as we seek the truth about what happened,” GM CEO Mary Barra said in a statement Thursday. “It was a difficult decision, but I believe it is best for GM.”

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