Türkiye is calling on Germany to investigate Monday's fire, which killed four Bulgarian citizens of Turkish origin in Solingen, diplomatic sources said Thursday, stressing that suspects should be brought to justice after reports that the fire could have been arson.

Noting that Türkiye's consul general in Dusseldorf, Ali Ihsan Izbul, and other officials have been closely monitoring the matter, the diplomatic sources said the country's ambassador to Berlin, Ahmet Başar Şen, will also visit those injured in the fire.

The fire that claimed the lives of a Turkish-Bulgarian family in Solingen was apparently an arson attack, German authorities said on Wednesday.

During the preliminary investigation, "clear remains of an accelerant" were found in the wooden stairwell of the four-story house, indicating that a "deliberate arson" could be the cause of the fire, Wuppertal's public prosecutor Heribert Kaune-Gebhard told reporters.

But he also noted that so far, they have not found any evidence of a racist or "xenophobic motive" behind the suspected arson.

The fire at the four-story house in western Germany claimed the lives of a man, his wife and their two children, who were Bulgarian citizens of Turkish origin.

As many as 21 people were rescued from the building, with nine taken to the hospital with serious injuries, including two in critical condition. Turkish nationals were among those injured.

According to the fire department, the blaze broke out in the early hours of the day on the first floor and quickly went out of control. The victims were believed to have been trapped on one of the upper floors when the aging structure's wooden stairs burst into flames.

Three decades ago, a far-right arson attack took place in Solingen, killing five members of a Turkish immigrant family.

Their house was set ablaze by neo-Nazis amid growing resentment against foreigners in the country after the unification of East and West Germany.