A wealthy Texas teen who had been a fugitive after breaking his probation sentence for killing four people while driving drunk, will be returned to the United States after being caught in Mexico, Mexican authorities said on Tuesday.

Ethan Couch, 18, and his mother, Tonya Couch, were taken into custody on Monday evening in the Pacific Ocean resort of Puerto Vallarta, the Jalisco State Attorney General's Office said in a statement.

Officials at the U.S. Embassy in Mexico City declined to comment for privacy reasons, saying only that they would provide any necessary consular assistance.

In Texas, Tarrant County Sheriff Dee Anderson said Couch will be placed in a juvenile detention facility once he returns to the United States and that an arrest warrant was issued for his mother.

Anderson said "intelligence information" indicated that Couch and his mother had driven across the border.

Through interviews, investigators learned that "what we suspected all along had happened, that they had planned to disappear, that they even had something almost akin to a going away party before they left town," he said.

"Our suspicion that his mother was assisting and helping him was proven true, we believe," Anderson said.

Anderson said he hoped that Couch's case would now be transferred to an adult court.

Ethan Couch's attorney, Reagan Wynn, said in a statement that he has not had the chance to speak with his client and does not expect to be able to until Couch is back in the United States. "Until we have more information concerning this situation, it would not be prudent for us to make any further public statement," he said.

Couch became known in the United States as the "affluenza" teen during his trial in juvenile court over the 2013 deaths, when a psychologist said he was so wealthy and spoiled he could not tell the difference between right and wrong.

He has been serving 10 years probation for intoxication manslaughter, a sentence critics saw as far too light.

Couch and his 48-year-old mother disappeared earlier this month, prompting officials in Tarrant County, Texas, to issue a warrant for his arrest.

The two were captured at the crossing of two streets near the popular Malecon, or boardwalk, in Puerto Vallarta. A police booking picture from Mexico showed the previously blond Ethan Couch with dark hair.

Mexican authorities said they had been working with the U.S. Marshals Service since Saturday to locate Couch and his mother.

Police handed the pair over to Mexican immigration authorities for being in the country without the proper permission so they could be returned to the United States, the Jalisco attorney general's office said.

Couch, then 16, was speeding and had a blood-alcohol level of nearly three times the legal limit when he lost control of his pickup truck and fatally struck a stranded motorist on the side of the road and three people who had stopped to help.

Several passengers riding in Couch's vehicle were hurt, including one friend who was permanently brain damaged.

Tarrant County began investigating this month after a video on Twitter appeared to show the teen among a group around a table littered with plastic cups and cans of beer in a game of beer pong. That would have been a violation of his probation, the Tarrant County District Attorney's office previously said.

Tarrant County Sheriff Anderson said last week it was possible Couch and his mother had fled the country. He said the home they shared had been cleared of its contents.

Their passports had been reported missing by the teen's father, who has cooperated with investigators.

U.S. Marshals had offered a $5,000 reward in exchange for his whereabouts.