A family of six was discovered inside a remote farm in the Netherlands, where it is believed they lived in isolation for nine years, according to CNN affiliate NOS.

The father and five children, ages 18 to 25, were found in the small village of Ruinerwold, in the northeastern province of Drenthe, Dutch police told CNN. A sixth adult child had left and was the one who alerted police.

Although the village has just a few thousand residents, no one knew the family was there.

Police arrested a 58-year-old man who rented the property. Authorities said they are still trying to determine the link between the detained man and the family, and they believe the family has been living there since 2010.

A call for help

For almost 10 years, the family lived in an enclosed area of the property and didn’t venture outside — until this month when the eldest son left, NOS reported.

The son visited one of the village’s few cafes, Café de Kastelein, looking confused and unkempt, according to NOS. He came in and tried to order a beer one night but left as the cafe was about to close, cafe owner Chris Westerbeek told RTL Germany. He came in again another night but quickly left.

Westerbeek described him as having long hair, a long beard and wearing old clothes, NOS reported.

“Last Sunday, he came and he sat here on the terrace and he asked for help,” Westerbeek told RTL Germany. “So I tried to speak to him, didn’t get enough info about him, so I asked him to call the cops, the police, so we can help him further.”

The son told Westerbeek he had never been to school and had not visited a hairdresser in nine years, according to NOS.

In a statement Tuesday, local police said they went to the family home after the eldest son said: “he was worried about his family’s living conditions.”

An investigation is underway

A team of investigators scouted the area, conducted a neighborhood survey and even used a drone to map the house from above before entering and finding the family inside, local police said.

“It is unclear whether they stayed there voluntarily,” the police statement said.

The family wasn’t registered in government records. They have now been examined by doctors, the police said.

“Part of our investigation is to find out what the people in that house were doing exactly. There are still many questions to which we have no answer. The investigation is still going on. The people were brought to a shelter home where they are taken care of and where they will be asked to tell their story,” police spokeswoman Nathalie Schubart told RTL Netherlands.

Ruinerwold Mayor Roger de Groot spoke to the media Tuesday, saying he had “never experienced anything like this.” He added that investigators believe the mother in the family died several years ago, possibly before the family moved into the farm.

According to NOS, the family had no contact with the outside world during those nine years.

Dutch police said they found them in a small room on the ground floor. Aerial photos of the property show a well-tended garden with what appear to be vegetables planted in neat rows, and NOS reported the family also had a goat.

Aerial images of the property show three rooftops. Some of the doors on the buildings are covered with overgrown greenery.

The home was accessible by a bridge over a river that neighbors said was always gated and locked, NOS reported. One neighbor told NOS he once tried to get closer but turned back when he saw multiple cameras on the property.

Neighbors said they never saw the children — only one man who regularly drove by in a car, according to NOS.

Man being held

“We understand that everyone still has many questions. We have those, too,” Dutch police said in a statement, adding they have assigned a large team to investigate how the family came to be there and whether any offenses have been committed.

The 58-year-old man was arrested for failing to cooperate with the investigation, Dutch police said.

He has a court appearance Thursday and is suspected of being involved in illegal deprivation of liberty and harming the health of others, the regional public prosecutor said on Twitter.