Three grandchildren of Southern California Rep. Gary Miller who were reported missing are with their mother, possibly in Nevada, and are believed to be safe, authorities said Tuesday.

Jennifer Dejongh was supposed to drop her three sons off at Miller's house Sunday for an "extended visit," according to court papers. Dejongh's father, Jude Lopez, said his daughter is in a custody dispute with the children's father, the congressman's son Brian Miller. The two were never married, he said.

Investigators were called because Dejongh "was supposed to show up with the kids at an agreed-upon location and she did not," said Steve Whitmore, a spokesman for the Los Angeles County Sheriff's Department.

"This is known as a child abduction. They're with their mother," said Whitmore. The children were not believed to be in immediate danger. No Amber Alert was issued, he said.

Sheriff's Deputy Bill Brauberger said the children may have been taken to Las Vegas or elsewhere in Nevada.

Sheriff's spokesman Deputy Tony Moore said he did not know if a warrant had been issued for Dejongh's arrest. Even if one hasn't, she is still subject to arrest by any law enforcement officer, Moore said, because she is in violation of a court order.

Lopez said his daughter told him Sunday she would not be bringing the children to the congressman. He said his daughter had friends in Nevada, but he did not know where she was.

Dejongh, who was recently married and also goes by her maiden name, Jennifer Lopez, was apparently upset by a court notice she received Saturday that said the congressman was seeking increased custodial rights, her father said.

Gary Miller's spokesman, Scott Toussaint, did not immediately respond to phone and e-mail messages seeking comment on Tuesday. A message left with an attorney for Brian Miller was not immediately returned Tuesday.

Gary Miller, 59, represents the 42nd Congressional District, which includes the communities of Diamond Bar, Brea, Chino and Chino Hills.