A bus has exploded in the heart of Jerusalem, wounding at least 15 people, an Israeli rescue service said.
The incident has raised fears of a return to the Palestinian suicide attacks that ravaged Israeli cities a decade ago.
Israeli media said a man who was seriously injured and not carrying any identification papers was under investigation on suspicion he was responsible.
Police initially called the blast a terrorist attack but later said all options were being examined.
Fifteen people were wounded, including two seriously, the Magen David Adom rescue service said.
Images show fire and large plumes of smoke billowing from the back of the bus.
The blast comes amid a seven-month wave of Palestinian attacks, mostly stabbings, in which 28 Israelis and two Americans have been killed.
At least 189 Palestinians have been killed in that period. Israel says most of the dead were attackers, with the rest killed in clashes.
PA