Dutch police said on Thursday they had arrested a second man in the case of six people who were found in a remote Dutch farmhouse, which has been described as "isolated from the outside world".

The individuals were discovered on Monday in a small "closed off" room on the ground floor of the house after police received a tip-off from a young man who said he was "worried about his family's living conditions".

"Today we arrested a second suspect in the Ruinerwold investigation," Drenthe police said in a statement, adding the man was detained on suspicion of "unlawful deprivation of liberty".

"The arrested person, a 67-year-old man from Ruinerwold, is one of the six persons discovered this Monday in the house."

A 58-year-old man, who was paying the rent on the property, was arrested on Tuesday and charged on Thursday with unlawful detention and harming others' health.

He will remain in detention for at least two more weeks, prosecutors said.

The Austrian Foreign Ministry said the man was an Austrian citizen, originally from Vienna.

The farmhouse is in Ruinerwold, Drenthe province in the northeast of the Netherlands.

A police statement said it was not clear whether the people found in the house were held against their will.

It's thought they had been living there since 2010.

According to the police, those discovered said they were a family — a father with five of his children —all of whom indicated that they were aged over 18.

Local media reported the individuals have held apocalyptic “end of days” beliefs, but police could not confirm this information to Euronews.

They have been examined by a doctor and are being cared for.

The farmhouse is hidden behind trees away from the main road, accessible only via a bridge over a canal. Neighbours told regional television that no-one suspected a family was living there.

Some said they occasionally tried to approach the property but never entered. They sometimes encountered a man who was polite and had a dog.

Jans Keizer -- who told RTV Drenthe he and his wife offered his new neighbour flowers and a bottle of wine upon his arrival -- also said he subsequently thought things strange. "That gate by his bridge was always locked. You did not enter the yard. I once tried to look around with a neighbour one evening. Then we saw a camera hanging in a tree," he is quoted as saying.

Police say they want to do their research "thoroughly and carefully".

"We have started a Large Scale Investigation Team. Investigators are examining possible criminal offences under the leadership of the Public Prosecution Service," they said in a statement.