Lionel Messi's older brother was arrested in hospital after authorities said they found a gun in a blood-covered boat he claimed to have abandoned after an accident.
Matias Messi was warned he could face eight and a half years in jail if convicted of illegal possession of a firearm. According to The Sun, an investigating judge decided the 35-year-old should be remanded in prison after he is well enough to leave hospital.
The prison remand order, which was approved by Judge Andres Donnola, remains in effect until 23 December.
Matias underwent an operation for injuries including a broken jaw and facial cuts. He will have to inform the court before being given the all clear to leave hospital so a judge can decide whether to allow him to return home to recover or send him to jail pending the ongoing investigation.
The elder Messi was under police guard at the Sanatorio Parque, a private hospital in his native city of Rosario, Argentina. Matias was arrested 24 hours after he was helped ashore when he was found drifting in a motorboat on the Parana River before dawn on Thursday (30 November).
The Sun reported that Matias was formally arrested in hospital on suspicion of the illegal possession of a firearm. Police were forced to track him down at a number of addresses in Rosario and around the city.
Ignacio Carbone, Matias' lawyer, said his client checked himself into hospital after he injured himself when he struck a sandbank. Carbone also suggested the gun found on the boat may have been planted by police.
Matias' family denied he had a firearm in the boat in a statement released on Sunday (3 December), The Daily Mail reported. They added that he suffered injuries after crashing against the windscreen of the boat when it hit a sandbank.
State prosecutor Jose Luis Caterina rejected the notion that police could have planted any evidence, adding the police procedure had been "transparent, clear and legitimate". Caterina claimed the .380 handgun was found with six bullets inside and ready to be fired.
Authorities are trying to figure out who owns the boat as it is unregistered.
Lionel's older brother was order last year to teach football as part of a probation order after being caught with a gun in his car. He was accused of illegal possession of a weapon after an unlicensed .22 pistol was found in his Audi A5 during a stop in October 2015.
Matias was ordered to stay off drugs and drink and to pay a fine of around €470 (£415). His probation ended two months ago.