Ethan Couch's probation officer couldn't reach him this week, Couch's lawyers told CNN. Couch's mother, with whom the 18-year-old lives, is also missing, said Scott Brown and William Reagan.
Under the terms of his probation, Couch isn't supposed to lose contact with his probation officer, his lawyers said.
Their apparent disappearance comes shortly after a video turned up on social media that allegedly shows Couch at a party where alcohol is being consumed, CNN affiliate KTVT reported.
When asked to confirm Couch's attendance at the party, his attorneys told CNN's sister network HLN they "are aware that the probation authorities and/or the District Attorney's office are conducting an investigation to determine if Ethan has violated any of the terms and conditions of his probation. It would not be prudent for us to make any further statement on Ethan's behalf until the investigations are concluded and it is determined what, if any, action will be taken against him."
Jail time possible if probation terms violated
Couch's attorneys argued in 2013 that his parents, because they spoiled him, were partly to blame for the crash on a road in Burleson, south of Fort Worth.
Prosecutors had asked for 20 years behind bars, but a Tarrant County juvenile court judge sentenced Couch to a decade of probation. Couch was ordered into long-term mental health treatment, away from his parents' influence.
After his recent disappearance, a court ordered Couch detained, according to his lawyers. At the time of his conviction, prosecutors said Couch could face up to 10 years of incarceration
if he violated the terms of his probation.
The approach was met with widespread outrage and disdain, and the term "affluenza" was widely mocked.
On the night of June 15, 2013, Couch and some friends stole beer from a Walmart.
Hollie Boyles and her daughter Shelby left their home to help Breanna Mitchell, whose SUV had broken down by the side of a road. Brian Jennings, a youth pastor, was driving past and also stopped to help.
Couch plowed into them, killing them all. The crash threw two passengers out of the bed of Couch's truck, injuring both severely.
The parents of one of the injured teens, who suffered debilitating brain injuries, sued Couch's family for $2 million.
Three hours after the crash tests showed that Couch had a blood-alcohol content of 0.24, three times the legal limit. Couch's vehicle also struck a parked car, which then slid into another vehicle headed in the opposite direction.
Eric Boyles, Hollie's husband and Shelby's father, felt the judge had been far too easy on Couch and angrily spoke out against how Couch was treated.
"The primary message has to absolutely be that money and privilege can't buy justice in this country," he said.