One of the images being shared on the social media portal Twitter.
An unidentified type of explosion rocked central Budapest late on Saturday, causing injuries to two police officers nearby, police said in a statement on Sunday.
"The police have involved experts for the review of the area, interviewing witnesses and collecting data," the statement said. "The local and expert examination of the origins of the explosion and the review of the damage is under way."
Police said there were no further injuries from the explosion, which occurred around 10:30 p.m. local time (2030 GMT).
There have been no further comments from police nor the disaster relief agency. A government spokesman declined further comment on whether the explosion may have had anything to do with a deliberate attack.
Hungarian Prime Minister Viktor Orban has been a vocal opponent of immigration into Europe and has campaigned for a referendum about migrant resettlement quotas on the premise that immigration increases the terror threat in Europe.
In a campaign leaflet to reject the quotas, Orban cited the Paris attacks last autumn and the Brussels and Nice attacks to underscore the perceived links between immigration and terrorism.
Hungary has seen merely a trickle of migration since it sealed its southern border with Serbia with a razor wire fence last year.
Police cordoned off a wide area around the Oktogon square in central Budapest and told residents to leave the buildings nearest the blast, local media reported. The normally busy intersection was packed with eye witnesses, including tourists.
"I am here on holiday and I was here in the hostel across the corner, and I was getting ready for a party," Polish tourist Olivia Sehildt told Reuters.
"Suddenly I heard a big boom...I was looking through the window and I saw a lot of cars coming, police, firemen, and a lot of people coming to the street...the windows were broken and nobody knew what happened."
Hungarian Kadosa Bencsy said his first thought was it may have been a terror attack.
"First I got scared that what I heard was what I had feared and terror has struck Hungary too," he said at the scene. "I have to say frankly that I have been fearing such a thing for a while...the possibility is there, that anywhere in the European Union it could happen."
