Three grandsons of a congressman from California who were abducted in 2007 have been returned to the United States from Mexico, where they were living with his son's ex-wife, authorities said on Thursday.

"My wife and I are extremely relieved that after more than three and a half years our grandchildren have been found unharmed and returned safely to the United States," U.S. Representative Gary Miller said.

The Republican congressman, who represents parts of Los Angeles, Orange and San Bernardino counties, made his statement a day after the children's mother, Jennifer Lopez Dejongh, was arrested in Mexicali with help from the FBI.

Lopez Dejongh is the ex-wife of Miller's son, Brian Miller. Shortly before the children went missing in 2007, a Los Angeles Superior Court judge had ordered shared custody between Brian Miller, Lopez Dejongh and the grandparents.

The 34-year-old Lopez Dejongh was arrested on suspicion of unlawful flight to avoid prosecution, the FBI said.

Dejongh was charged in 2007 with three counts of child custody deprivation, said Sandi Gibbons, a spokeswoman for the Los Angeles district attorney's office. She is expected to appear in court on Friday on those charges.

The older boy is 11 years old and his younger brothers are 9-year-old twins.

Court California Mexico Fbi