DETROIT — Emails showing that General Motors ordered a half-million replacement ignition switches nearly two months before telling the government of a safety recall will be heavily scrutinized by federal prosecutors investigating GM’s conduct, according to legal experts.

The email chain, released Monday by an attorney suing GM, again raises questions about how forthcoming GM has been with safety regulators and lawmakers, as well as a GM-funded investigation into the defective switches by former U.S. Attorney Anton Valukas.

The chain of emails from December through February shows that a contract employee for GM inquired about the parts on Dec. 18, 2013, and ordered them from Delphi the next day, in preparation to replace parts on 500,000 to more than 700,000 vehicles. The cost was estimated at nearly $3 million.

Yet GM did not report a safety defect to the National Highway Traffic Safety Administration until 51 days later, on Feb. 7, 2014. Federal law requires automakers to tell the agency about defects within five business days of discovering them.

The U.S. attorney’s office in Manhattan is investigating potential criminal actions by GM in its handling of the recall of 2.6 million older-model small cars nationwide. The faulty switches have been responsible for at least 32 deaths and hundreds of injuries. The switches can slip out of the run position, causing engines to stall unexpectedly and disabling air bags. GM has admitted knowing about the problem for more than a decade.

The emails muddy the timeline GM has given regarding the recall. The parts order came just after a Dec. 17 meeting of a three-executive GM panel that decides if cars should be recalled. But the Valukas report said that although the committee heard a presentation from GM investigators seeking to recall the ignition switches, no decision was made that day. GM says it didn’t determine that the cars should be recalled until Jan 31.

Also, the parts order was not mentioned when CEO Mary Barra subsequently testified before Congress. Barra has said she first found out about the switch problem in late December and the decision to issue a recall on Jan. 31. GM says it is standing by Barra’s previous statements, but the emails could lead to further congressional hearings on the matter with Barra being called to Washington again.