A convicted sex offender on the Sonoma County Sheriff's Office most-wanted list, who fled the country in 2008 after he came under suspicion for child molestation, was in custody Tuesday.

William Dean Buchholz, 79, was apprehended Friday by the U.S. Marshals Service outside Mazatlan, Mexico, Napa County Sheriff's Capt. Tracey Stuart said.

His wife, Joan Kathryn Buchholz, 75, of St. Helena also was arrested and is suspected of financially supporting her husband while he was at large, Stuart said.

Authorities began looking for Buchholtz in 2008 when he failed to register his address with the Napa County sheriff's deputy in charge of tracking sex registrants, Stuart said.

Detectives suspect he fled the country to avoid arrest in Sonoma County, Stuart said.

Buchholz faces two charges of felony lewd and lascivious acts with a child younger than 14, according to the Sonoma County District Attorney's Office. The arrest warrant was issued in 2009 and lists an offense date of June 1, 2007.

Buchholz' wife told detectives at the time that she did not know where he was and did not help him escape, according to Stuart.

Nearly five years later, a Napa County detective reopened the case in April and found evidence at his wife's St. Helena home and in financial documents that she was paying her husband's credit card bills and had been in regular contact with him, Stuart said.

Joan Buchholz surrendered to authorities June 28 after a warrant was issued for her arrest in Napa County, Stuart said. She was released and is awaiting an October court date.

U.S. Marshals agents used financial records to track William Buchholz to Mexico. Buchholz was booked into the Los Angeles County Jail on Friday on warrants from Napa and Sonoma counties.

Stuart did not have details about the conviction that required Buchholz to register as a sex offender.

You can reach Staff Writer Julie Johnson at 521-5220, julie.johnson@pressdemocrat.com or on Twitter @jjpressdem.