A postmortem into the death of Russian oligarch Boris Berezovsky found the cause of his death to be "consistent with hanging", Thames Valley police have said.

The examination by a Home Office pathologist found nothing to indicate a violent struggle, a police spokesman said. Further tests are now due to be carried out on the body of Berezovsky, 67, who was found dead at his Berkshire home on Saturday.

Earlier a friend of the Russian exile had told the Guardian that Berezovsky had marks around his neck.

Nikolay Glushkov, who spoke to Galina Berezovsky after the businessman's ex-wife saw his body in the bathroom of the Berkshire mansion, said: "A scarf was there. There were traces of him being strangled around the neck."

Berezovsky was found by a bodyguard on Saturday after he had not surfaced since the night before. Family and friends who arrived at the house said there was no sign of blood and he was fully clothed. He had been suffering from depression after a shattering high court defeat last year to his former business partner, Roman Abramovich.

Thames Valley police would not comment on reports of items found at the scene.

Officers are set to continue examinations at the property this week and a cordon remained in place around the house on Monday night after Berezovsky's body had been taken away. In a statement on Monday lunchtime DCI Kevin Brown reiterated: "We have no evidence of any third-party involvement at this stage."

Galina Berezovsky – who owns the house where her ex-husband was living – and other members of the family have been interviewed by police and have been prepared for further questioning as police seek to piece together the last days of Berezovsky's life "to gain a better understanding of his state of mind" amid speculation that he may have killed himself.

The bodyguard, who was the only person at the house when the emergency services arrived on Saturday afternoon, was interviewed by police at length while still at the house and left early on Sunday.

Glushkov said he and some other Russian exiles did not believe Berezovsky killed himself. Instead, they think he may have been murdered. Yuli Dubov, another friend of Berezovsky, said he had arrived at the house at 5pm on Saturday – finally leaving 12 hours later. He was not allowed inside and waited in a police car. Galina was already inside the house with her two children and the bodyguard and detectives kept them in the kitchen. Dubov gave the bodyguard a lift back to London around dawn on Sunday.

"He told us that he came to the house at 3pm on Saturday," Dubov said. "He saw that there is Boris's mobile on the table. There are a number of unanswered calls. He got worried. He went upstairs and saw the door to the bathroom was closed. He broke the door and saw Boris on the floor. He touched the hand. The hand was cold. He called the police."

Dubov added: "The bodyguard was a well-trained person. He closed the bathroom and never went near the body again. He knew what you should and should not do at a crime scene."

A close friend of Galina, Sasha Nerozina – who is the author of a spy thriller called KGB Girl in which a "famous Russian oligarch in exile … is assassinated in his countryside mansion outside London" – said Berezovsky's family had been distressed by speculation in Russia about the cause of his death.

"They are trying to be as quiet as possible and grieve on their own," Nerozina said. "For the children it is the most tragic time. They are extremely shocked and devastated. If you look at Russian TV some are saying he was killed, some are saying he may have staged his own death to appear as if it came from Putin's hand. There are a lot of conspiracy theories and when you lose someone you love, you don't want them to interfere with your grief."

She continued: "I write books about it, but I am not suspicious in this particular circumstance. He was not in anyone's way, he wasn't presenting opposition to anybody or preventing anyone's business.

"It would have been a waste of time for the Russian secret service to go after him. If it would have happened it would have happened earlier when he was at the height of his significance."