Attorneys for a Texas teenager known for using an "affluenza" defense said Tuesday that they're investigating whether the 18-year-old fled to Mexico or was taken against his will.

Ethan Couch's attorney, Scott Brown, said after a hearing in the case that whether his client "was voluntarily or involuntarily taken to Mexico is something that is still being investigated." Authorities allege that Couch and his mother fled to Mexico as Texas prosecutors investigated whether he may have violated his probation in case stemming from his drunken-driving wreck that killed four people in 2013.

Tuesday's juvenile court hearing was scheduled to determine whether Couch, who is being held in Mexico, violated his probation and if the case should be transferred to adult court. But the judge delayed the hearing shortly after it started, after Couch's attorneys said his parents weren't properly notified. Another hearing wasn't immediately scheduled.

The drunken-driving case drew widespread derision after an expert called by Couch's lawyers argued he had been coddled into a sense of irresponsibility by his wealthy parents, a condition the expert called "affluenza."

Couch was 16 at the time and driving at three times the legal intoxication limit for adult drivers. Investigators said he rammed his pickup truck into a crowd of people trying to help a stranded motorist.

A juvenile court judge gave the teen 10 years' probation, outraging prosecutors who had called for him to face detention time.

Authorities apprehended Couch and his mother, Tonya Couch, last month in Puerto Vallarta, Mexico. Tonya Couch was quickly deported and has been released on bond in Texas. The 48-year-old is charged with hindering the apprehension of a felon.

Ethan Couch remains in a Mexico City detention facility, where he is contesting his deportation.