None of the detainees were arrested.
Rita Stundienė, spokeswoman for the Prosecutor General's Office, told BNS that the young men may be imposed a fine or sentenced to up to two years in prison for instigating discrimination and up to three years in prison for vandalism.
In Stundienė's words, the suspects are members of an "informal ultra-nationalist international organization."
Vilnius police told BNS that the police had requested detention of one of the suspects, but the court overruled the motion.
The suspects are to be released on Friday on a pledge not to leave their place of residents, some of them will have their IDs confiscated.
The five men were detained for 48 hours on Wednesday following a series of searches.
"Items and documents important for the pre-trial investigation were taken," the police said in a statement.
Last Saturday, the police received a report that a poster saying "Tomaševski Stop Doing Damage to Lithuania Or Your Place Will Be Here" was found near the grave, and later on, a carton box was also found with inscriptions "Poles Will Die", "Call the Cops", "Careful, Bomb" and "TNT".
Valdemar Tomaševski is the leader of the Electoral Action of Poles in Lithuania.
Pilsudski is credited for his contribution to the restoration of Poland's independence after World War One. But for many Lithuanians, Pilsudski brings negative associations due to his involvement in the occupation of Vilnius Region. His body is buried in Krakow, but his heart is in Vilnius.