Ex-“Teen Mom” star Jenelle Evans‘ oldest son has disappeared one too many times for authorities not to investigate the adults in his home — which we’re told they’re now officially doing.

Law enforcement sources tell TMZ … Jenelle and her husband, David Eason, are currently under investigation for child neglect after 14-year-old Jace‘s latest disappearance.

Remember, he was reported as a missing person last week … and, thankfully, he was found soon after. However, he’d reportedly already gone missing twice before that — something Jenelle has attributed to him just being a rebellious teen.

Sources with direct knowledge tell us it could be much more serious than that … and the reason Jenelle and David are in investigators’ crosshairs is because Jace apparently told cops David allegedly assaulted him.

We’re told that after this most recent fleeing attempt … the kid was found to have visible marks on his neck and arm. Our sources also say the alleged assault is believed to have gone down at someone else’s home, and there’s Ring camera footage that police and CPS now have in their possession.

Of course, if there’s any evidence of physical abuse … the current investigation could lead to serious charges. For the time being, though, it’s just an investigation for child neglect.

Jenelle had Jace with her first baby daddy, Andrew Lewis … but we’re told she has primary custody — and has for years now. Some have questioned whether that should remain the case, amid all these troubling developments.