Former Brazil and Barcelona player Ronaldinho is adapting quickly to life in a Paraguayan jail, the head of the facility told Reuters on Monday, but his lawyers are hopeful he may soon be released into house arrest while the investigation continues.

"In broad terms he is doing very well," prison warden Blas Vera told Reuters in a telephone interview. "I see he is in good spirits, just like you see him on television, always smiling."

Vera said that Ronaldinho and his brother Roberto Assis, who were arrested on Friday for using a false Paraguayan passport, would present their case to a judge on Tuesday.

Their lawyer Sergio Queiroz told Reuters they had asked a court to release them into house arrest and offered guarantees they were not a flight risk.

Vera said the 39-year old former AC Milan and Paris Saint-Germain forward and his brother had beds, a television and a fan in their cell at the prison on the outskirts of the capital Asuncion.

The brothers use a communal bathroom and have the right to use the outdoor patio on a regular basis.

The pair's lawyers have provided them with meals and they have not eaten the food offered by the jail.

The maximum security facility has around 195 detainees, including politicians and police officers accused of corruption as well as major drug traffickers.

The more dangerous prisoners are housed in a different wing to Ronaldinho, Vera said, adding that he was working to ensure the pair's stay is "as comfortable as possible."

Carlos Gamarra, the former captain of Paraguay's national team who also played for several Brazilian clubs, visited Ronaldinho with a group of ex-players in jail on Sunday.

Vera said others who were at the regular Sunday visiting time befriended the Brazilian.

"There was also a group of boys and girls and he welcomed them, gave them hugs and chatted with them," he said.

Ronaldinho, who was last year named a tourist ambassador by Brazil's far-right government, arrived in Paraguay on Wednesday, invited to the landlocked South American nation by a local casino owner.

Although he last played professionally in 2015, Ronaldinho, who also represented Brazilian clubs Atletico Mineiro, Flamengo and Fluminense, is still hugely popular with global football fans and advertisers.

He won the World Cup with Brazil in 2002 and the Champions League with Barcelona in 2006. He was also named FIFA world player of the year in 2004 and 2005.