Chris Westerbeek first noticed something was wrong when a stranger walked into his bar with a confused look on his face, for the second time that week.

Key points: The family was discovered after one of the male siblings escaped to a local pub, where he drank five beers

The family was discovered after one of the male siblings escaped to a local pub, where he drank five beers The bartender was alarmed over the man's dishevelled and confused appearance and called the police

The bartender was alarmed over the man's dishevelled and confused appearance and called the police Police tracked down a remote, boarded-up farmhouse and found a secret space hidden behind a large cupboard

It wasn't long after the 27-year-old Dutch bar owner began speaking to the man that he realised he was in need of help and called the police.

Police subsequently found five siblings and a man they identified as their ailing father locked away in a secret room at an isolated farm near Ruinerwold, a village in the northern province of Drenthe in Holland.

Mr Westerbeek said the first time the man walked into his bar he ordered a couple of beers, paid for them and walked away.

The second time he didn't order anything and asked the bar owner for help.

"To me he [didn't] say much, only that he needs help and that he can't go home anymore. From that time I thought yeah we have to call the police," he told ABC's The World Today.

Cafe owner Chris Westerbeek told RTV Drenthe one of the family members came into the cafe looking confused. ( RTV Drenthe )

Loading

The man waited out the front of the bar while Mr Westerbeek called the police.

Mr Westerbeek said he didn't say much, hardly made eye contact and didn't answer many of his questions.

"We found six people living in a small space in the house which could be locked. Not a cellar. It is unclear if they resided there voluntarily," local police said in a statement, adding that the people may have been hidden away on the property for nine years.

"They say they are a family, a father and five children."

Officials did not confirm local TV reports that the family may have held "end of days" apocalyptic beliefs.

Earlier, local mayor Roger de Groot said a 58-year-old man, not the father of the children, had been arrested. His role was unclear.

The Dutch newspaper Algemeen Dagblad identified the man as "Joseph B", an Austrian carpenter.

Police confirmed they had arrested a man who was renting the farm but would not comment on his identity.

The children's mother had apparently died before they moved to the farm, the mayor said.

Mr De Groot said the family was now, "in a safe place receiving appropriate care and attention".

None of the family members were registered as residents with the municipality, police said.

Mr Westerbeek said the young man who visited his bar was about 25, with long hair, and appeared scruffy and bewildered.

He was wearing 1970s style clothes and seemed shy and disorientated, Mr Westerbeek said.

He said he had not been outside for nine years.

"You could see he had no idea where he was or what he was doing," Mr Westerbeek, said. "He said he had run away and that he urgently needed help.

"[From] the way he spoke and how he looks at you ... you can see that he needs help."

In the living room of the farmhouse, hidden behind a large cupboard, police found an entrance to a secret space.

The siblings had apparently lived in makeshift rooms and survived partly on vegetables and animals from a secluded garden on the property, local TV RTV Drenthe reported.

"I understand there are a lot of questions," Mr De Groot said.

"We have many too. The police are investigating all possible scenarios."

Drone images of the farm showed a cluster of buildings with a large vegetable garden on one side.

The small property appeared to be ringed by a fence and largely obscured by trees.

ABC/Wires