Four people have been arrested in connection with the kidnapping of newborn twins in Michigan.

The twins -- identified by police as Montana and Matthew Bridges -- were safely returned on Tuesday, according to Detroit police.

The twins were the subject of an Amber Alert on Aug. 21 and the case will be submitted to the Wayne County Prosecutor's Office.

The babies were dropped off at a precinct and then taken to the hospital to be evaluated.

"They are in good condition," Detroit Police Chief James White said during a press conference Tuesday.

A mother reported her 14-day-old children missing from a Quality Inn hotel in Livonia, Michigan, on Monday night, according to Livonia Police Capt. Gregory Yon.

"The lady left them with two friends and when she came back they were gone," Yon said.

Police did not reveal why the children were abducted, but said they were stable and did not have any obvious injuries.

"They were safely brought inside the precinct, made contact with an officer at the desk," White said. "The entire precinct was on high alert."

"To see them walk in with the two babies, we were all very happy," White said.

The investigation into the incident is still ongoing.

The prosecutor's office told ABC News that the case is being reviewed and no charges are expected to be filed on Wednesday.