The police will decide early this week whether or not the suspect would be placed in remand.
The suspect had a criminal history of similar incident, said the police.
A total of 20 buses burned early Saturday morning in the industrial area at Runosmäki, Turku.
In addition, the second part of the two-part depot building was completely gutted in the blaze, incurring millions of euros of financial loss, estimated the police.
The police interrogated witnesses and spoke of their tactical and technical investigations.
The case is being investigated as aggravated property damage.
