'Terrorist attack' foiled
Rosenfeld said they found a "large explosive" inside the vehicle and called in bomb-disposal teams.
"We heightened security in and around the Haifa area searching for a number of possibilities, people or vehicles that have left the area," he said.
"The high level of security is continuing as well today to prevent any further attacks."
Olmert said the occupied West Bank had long been a "stepping off point" for attacks inside Israel.
"A preliminary investigation shows it was a terrorist infrastructure operating with great sophistication and aiming to carry out a mass-casualty attack," he said.
"A premliminary investigation shows it was a terrorist infrastructure ... aiming to carry out a mass-casualty attack"
Israeli prime minister
The number of Palestinian attacks from the occupied West Bank has dropped over the past several years, a decrease Israeli leaders attribute partly to the barrier Israel has built in the territory despite international condemnation.
Olmert said: "We should not delude ourselves. Attempts by terrorist organisations to carry out attacks inside Israel, along its borders and in its heartland, in various regions, are continuing."
There was one Palestinian suicide bombing in Israel last year.
In four other incidents since 2008, which police described as attacks, three bulldozers and a car driven by Palestinian residents of occupied East Jerusalem rammed into Israeli vehicles in the western part of the city.