Saturday morning, the current prime minister Stefan Löfven and Social Democratic party secretary Carin Jämtin took part in a wreath-laying ceremony at Palme's grave in Adolf Fredrik's church in central Stockholm.
The continuing police investigation involves five staff, who are examining 250 meters of shelves of evidence, which is constantly growing.
"We receive about two or three tips a week, which we compare with old information to see if it adds anything new," the investigation group's chief Hans Melander said on the police's website.
In July 1989, Christer Pettersson was convicted to life in prison for murder, but the Svea Court of Appeal later released him. Pettersson died in 2004.