The Stasi set up its investigation into Palme's death just hours after he was killed in Stockholm on 28th February 1986, Expressen reports. After a few months the East German investigators identified a suspect: Amir Heidari, a Swedish resident claimed to be at the head of one of Europe's largest people-smuggling rings.
Stig Edqvist, the head of the Swedish police investigation into Palme's killing, said he knew nothing about the Stasi inquiry.
"This is news to me," he told Expressen.
The documents in the Stasi's archive about the investigation into the Palme murder were uncovered by historian Leif Björkman. The material includes a detailed report on their suspect's background and a copy of his passport, showing he travelled to Stockholm on the day Palme was killed.
Edqvist said Heidari was questioned about the murder by Swedish police, but he had an alibi for the night of the murder:
"We questioned him. A number of people said they were with him here in Sweden on 28th February and 1st March. He was therefore quickly ruled out."
Officers on the Palme investigation are keen to see the Stasi archive material, Edqvist said.
Heidari is currently serving a jail sentence for people smuggling. He told Expressen that he could prove he had nothing to do with Palme's killing.