At least 27 people died and 180 others were hospitalized after an explosion and fire at a Bucharest nightclub with hundreds of people inside, government officials said.
It was one of the capital's worst incidents in decades.
The death toll may still climb at the Colectiv club, which hosted a rock concert attended by up to 400 people on October 31, Deputy Interior Minister Raed Arafat said.
Romanian President Klaus Iohannis said there are "indications" that failure to follow safety regulations may have played a part in the tragedy.
"We already have indications that the legal regulations had not been respected," Iohannis said. "I hope that the authorities manage their inquiry with speed and rigor."
One witness said there were fireworks inside the club. A pillar and the club's ceiling caught fire, and then there was an explosion and heavy smoke.
TV footage showed police officers and paramedics from a mobile hospital trying to resuscitate young people lying on the pavement while sirens wailed with more ambulances deployed to the scene.
"There was a stampede of people running out of the club," a man who escaped told Reuters.
Deputy Prime Minister Gabriel Oprea said an investigation into the causes of the incident is under way.