The Georgian Prosecutor General's Office said experts who had examined Arutyunyan concluded these were thermal injuries that could have been caused by hot water in the bathroom, the only place where the detainee had not been observed.
Law enforcement authorities are sure Arutyunyan was injured deliberately, whereas he said it was a mosquito bite.
Arutyunyan's prison cell is equipped with surveillance cameras.
The 27-year-old resident of Tbilisi killed a police officer during his arrest on July 21 in the capital of Georgia.
Arutyunyan is accused of attempting to carry out a terrorist act, intentional homicide, and the illegal manufacture, storage, and use of weapons.
Right after his arrest, Arutyunyan confessed he had thrown a hand grenade toward the platform where the U.S. and Georgian presidents were standing. He also said he was ready to repeat an attack on President Bush.
Arutyunyan may be sentenced to life in prison if found guilty.
