A mezzanine floor has collapsed at the Jakarta stock exchange building (IDX), injuring dozens of people.
Dramatic CCTV footage captured the moment of collapse, which sent a group of more than 30 students gathered on the mezzanine crashing into the lobby.
The area was evacuated and cordoned off by police, but trading has now resumed.
Police say 72 people were hurt and are being treated in three different hospitals in Jakarta, but there have been no fatalities.
Police spokesman Argo Yuwono told local media that some of the victims, who had injuries to their hands and feet, had been taken to nearby hospitals.
Rebecca Henschke, BBC News, Jakarta
Police using dogs and riot gear have pushed journalists back from the lobby area where the roof collapsed. They say it was not a terrorist attack, but they are still investigating what caused the floor to collapse. Fifteen ambulances have left the scene carrying the injured, officers say.
It happened during most people's lunch break so the building was quieter than usual, but there were still hundreds of people there.
The Jakarta stock exchange is a grand two-tower building with a vast marble floor lobby. The Indonesian government has being pushing for more foreign investment, but today's chaotic scenes here are not the image they want to portray.
Mr Argo told Metro TV: "We are still investigating the cause, but for now our priorities are the casualties."
The incident happened shortly after 12:00 local time (05:00 GMT), according to a journalist from Metro TV who was in the building.
Marlia Zein added that there was a "loud banging", leading people inside to "immediately" run out of the building.
A student named as Alfita, who was on the walkway when it collapsed, told Reuters news agency: "There was a rumbling noise but it wasn't an explosion.
"It was like something had fallen, and suddenly the floor we were standing on fell away."
The stock exchange has re-opened for the afternoon session, with exchange chief Tito Sulistio saying the system was "not affected".