The Secret Service officer was wearing a bulletproof vest, but sources say investigators haven’t found the fragment that pierced it — and can’t definitively say whether it came from the suspect.

The FBI has not found the fragment that pierced a Secret Service officer’s bulletproof vest at the White House Correspondents’ Dinner on Saturday, leaving investigators unable to say for certain whether the armed attacker shot the officer or how he was injured, according to two people briefed on the probe.