He crossed his hands above his head as he finished the race - a gesture made by Ethiopia's Oromo people who have suffered brutal police crackdowns.
He says he may be killed if he goes home but Ethiopia's government says he will be welcomed as a hero.
However, state media is not showing photos of him crossing the line.
There has been a wave of protests in Ethiopia in recent months over a series of frustrations, including attempts by the governments to reallocate land in the Oromo and Amhara regions.
US-based Human Rights Watch says security forces have killed more than 400 Oromo protesters, a figure the government disputes.
Rule 50 of the Olympic charter bans political displays or protests and the IOC say they are gathering information about the case.
The BBC's Emmanuel Igunza in neighbouring Kenya says Mr Feyisa is being described by some as the bravest Olympian at the Rio Games for his anti-government protest, but he now faces the prospect of a life in exile.
Within hours of his protest, a crowd-funding page was set up, saying the runner had displayed "extraordinary heroism" and that he had become an "international symbol" for the Oromo protests.
The California-based organiser had initially set a target of $10,000 but it was exceeded within an hour.
"We raised the bar to $25,000 and that too was exceeded in a few hours," Solomon Ungashe wrote on Facebook.
After the race, Mr Feyisa explained why, as an Oromo, he supported the protests about land and resources.
"The Ethiopian government is killing my people so I stand with all protests anywhere as Oromo is my tribe. My relatives are in prison and if they talk about democratic rights they are killed," he said.
A legal team hired by Ethiopians in US is headed to Rio to try and help Mr Feyisa, who has a wife and two children in Ethiopia, with a request to seek asylum in the US.
But Information Minister Getachew Reda told the BBC the government had no reason to arrest him and it respected his political opinion.
He also said none of Mr Feyisa's relatives had been jailed over the Oromo protests.
Ethiopian state-owned television station EBC Channel 3 covered the race live, including the finish, but did not repeat the clip in subsequent bulletins - focussing instead on the winner Kenya's Eliud Kipchoge.

Adrian Brown, 38, experienced a "severe psychotic episode" when he stabbed Muhammed Ali on a London Overground train on 12 December 2016.
Judge Deborah Taylor QC ordered that Brown should be detained indefinitely.
She added he would only be released on the order of a judge or the government.
Brown, of Brockley Rise, south-east London, appeared via video link from Broadmoor Hospital during the hearing.
A jury found Brown not guilty following a two-day trial at Southwark Crown Court.
He was also found not guilty, by reason of insanity, of possession of an offensive weapon and of assault by beating of Mr Ali.
The trial heard Brown had been delusional in his belief he would "save humanity" and exorcise a Muslim demon haunting him by stabbing his victim.
The court was told he was heard by other passengers to say "Where are all the Muslims? I am going to kill all the Muslims", before holding a knife to the throat of another woman, who was unhurt.
Brown accepted carrying out the attack but pleaded not guilty to a charge of attempted murder on the grounds of insanity.
Mr Ali had been travelling home with his wife when the assault took place between Honor Oak Park and Forest Hill, south London.
He told court that the attack had left him too frightened to leave his house.
"I struggle to sleep at the time because every time I shut my eyes I have flashbacks to the whole thing", he said.
"I can only assume it was me because my wife was wearing a headscarf."
Detaining Brown indefinitely under section 37 of the Mental Health Act, Judge Taylor said: "You have a long history of psychotic illness and on that day you were suffering and you continue to suffer from paranoid schizophrenia.
"There's no doubt that if it had not been for the prompt intervention of an off-duty police officer and two medical practitioners that he he may well have died such were the severity of his injuries and the loss of blood."
A crowd-funding campaign has raised more than $40,000 (Â£30,000) to help Ethiopia's Olympic marathon silver medallist Feyisa Lilesa seek asylum.
[NEXT_CONCEPT]
A man with schizophrenia who repeatedly stabbed a train passenger after yelling "I want to kill all the Muslims" has been found not guilty of attempted murder by reason of insanity.