Eight people were killed during a fatal fire in Paris on early Wednesday, according to officials. The case is still under investigation, as it is unknown whether it was an act of arson.

Pierre-Henry Brandet, spokesman for the Interior Ministry, said two children were among those who were killed during the fire while four survivors were rushed to the hospital, according to CBS News.

A small fire at an apartment building located at the foot of Montmartre hill broke out around 12:23 a.m. (GMT), that was quickly put out by firefighters. Two hours later they were called back to the scene because another fire started at the ground floor stairwell that eventually spread out to the building's upper floors. 100 firefighters were needed to put the fire down, the Los Angeles Times reported.

"It's clear that when you have two call-outs in the same night... this could be a malicious act," Brandet said, according to BBC.

Criminal prosecutors are conducting the investigation at 4 Rue Myrha, as authorities are under the impression that the fire may have been started on purpose. Interior Minister Bernard Cazeneuve announced that it is still "too early to determine the causes of this tragedy," according to the Business Standard.

The building is a private one, and some of the building's tenants reportedly tried to escape the fire through the windows.

"On behalf of the Paris citizens and myself, I would like to give my sincere condolences to the families and relatives of the victims," Paris Mayor Anne Hidalgo said, according to CNN. "I want to tell them that, this morning, Paris is mourning."

The fire was put under control on Wednesday morning.