According to ESPN, the former Rockets player was arrested in Houston overnight when a handgun was allegedly observed in the seat of a car that Harden owns.
Two people have been arrested in connection with the investigation.
The arrest comes weeks before he was to surrender to go to federal prison after being convicted of COVID-related fraud.
A man was charged after authorities say he brought an explosive device and other weapons through a security checkpoint at a California airport.
Dunn Police Chief Lynn Gay said the investigation was launched after the baby died Monday at a hospital.