Media playback is unsupported on your device Media caption "It was 24/7 loud music, or, if they showed appreciation or enjoyment of the music... loud static", said Roberto Villasenor, Tucson Police Department

Police in Arizona say three sisters were held captive in filthy conditions for up to two years by their mother and stepfather in the city of Tucson.

Investigators say two of the girls, aged 12 and 13, escaped and alerted a neighbour after their stepfather tried to attack them with a knife.

Officers then found a 17-year-old locked in her bedroom.

The girls were malnourished and dirty and told the police they had not taken a bath in up to six months.

"They were kept in filthy living conditions separately and told patrol officers that they had not seen each other in almost two years," Tucson police captain Mike Gilooly told reporters.

Loud music

Stepfather Fernando Richter, 34 , and mother Sophia Richter, 32, have been charged with emotional and physical abuse and three counts of kidnapping. The stepfather was also charged with sex abuse.

Image caption The younger girls are said to have escaped through a window on Tuesday

The girls were allegedly held under 24-hour surveillance, with an elaborate alarm system and soundproofing of rooms.

"Their movements were controlled - when, where and how they went to the bathroom, when they were fed," said Tucson Police Chief Roberto Villasenor.

Loud music was continuously played in the girls' bedrooms and towels had been stuffed into ducts and under the doors in an apparent attempt to muffle sound, Police Chief Villasenor told a news conference.

The girls have been removed from the house and are under the care of child protection services.

The two younger girls escaped through a window on Tuesday after their stepfather tried to break down a door while brandishing a knife, police said.

Investigators are examining a diary kept by the older sister during her alleged captivity.

They are also trying to establish if and where the girls went to school.

During a brief court appearances on Wednesday, neither parent entered a plea.