JERUSALEM — Israeli police stepped up security measures in Arab neighborhoods in east Jerusalem on Monday, searching trucks and arresting relatives of the Palestinian truck driver who rammed his vehicle into a crowd of Israeli soldiers at a Jerusalem tourist spot the previous day, killing four soldiers and injuring 17 others.

Nine people were arrested, five of them relatives of 28-year-old Fadi Qunbar, the attacker. All arrested were from the Jabel Mukaber neighborhood of east Jerusalem where Qunbar lived, police said.

Police forces checked drivers and searched parked cars and trucks throughout east Jerusalem in an effort to prevent copycat attacks, police spokesman Micky Rosenfeld said.

An investigation is underway as to how Qunbar managed to make his way on Sunday to the Jerusalem promenade where the soldiers gathered; who owned the truck he drove and whether he planned his attack ahead of time, Rosenfeld said.

Police used concrete slabs to block some entrances of Jabel Mukaber, and a police officer checked cars leaving it. Israeli special forces dismantled a mourning tent erected to receive visitors paying respects for Qunbar, who was fatally shot at the scene of the attack. Overnight, police say, Palestinians shot fireworks at Israeli forces at a police post near the neighborhood.

Israeli Prime Minister Benjamin Netanyahu said authorities would increase the number of concrete barricades along Jerusalem roads where pedestrians gather.