An explosion tore through a bus in Jerusalem on Monday and set a second bus on fire, wounding 16 people in what an Israeli official said was a bombing.
Israeli media said a man who was seriously injured and not carrying any identification papers was under investigation on suspicion he was responsible.
Suicide bombings on Israeli buses were a hallmark of the Palestinian revolt of 2000-2005 but have been rare since. A bomb left by an Israeli Arab aboard a Tel Aviv bus during the 2012 Gaza war caused injuries but no deaths.
Police initially said they were looking at the possibility that a technical malfunction caused the fire in Derech Hebron, an area in southwest Jerusalem close to the boundary with the Israeli-occupied West Bank.
But a spokeswoman for Nir Barkat, the Israeli mayor in Jerusalem, said the explosion was a detonation.
"It was small, but it was definitely a bomb".