Five people were injured in an explosion on an overpass near an Istanbul metro station during the Tuesday evening rush hour, the district mayor said, halting some train operations and heightening security fears.
Turkey has been on high alerts since more than 100 people were killed twin blasts at a peace rally in Ankara in October and a similar attack in Suruc, near the Syrian border in July that left 33 dead.
Tuesday's blast near the Bayrampasa metro station came at the height of the evening rush hour, district Mayor Atilla Aydiner told A Haber television. Aydiner said the cause was a pipe bomb, Reuters reported.
Authorities suspended services to the station immediately after the explosion. Bayrampasa is a residential and industrial area on the European side of Istanbul.
While Haberturk TV initially reported that one person died in the explosion, Aydiner confirmed only five injuries. Istanbul Governor Vasip Sahin said that only one person was slightly injured.
Turkish authorities have yet to release details about the incident, other than to say that the official cause of the explosion was still not known. Grainy CCTV footage showed a large flash of light on the overpass followed by what appeared to be showers of burning embers falling to the ground as cars drove below.
Haberturk TV reported that a power transformer may have caused the blast, but the report could not be confirmed.
Although Istanbul's metro is largely underground, it runs above ground in some places, including around Bayrampasa. Photographs on social media showed what appeared to be dozens of people walking alongside overground train tracks after trains had been halted.
Turkey, a NATO member, has carried out air strikes against in neighboring Syria as part of the U.S.-led coalition fighting the Islamic State in Iraq and the Levant (ISIL).
It also faces threats from the outlawed Kurdistan Workers Party (PKK) and the far-left Revolutionary People's Liberation Army-Front (DHKP-C), which is believed to have attacked the U.S. Consulate in Istanbul in August.
Al Jazeera with Reuters