Authorities have arrested two male minors in connection with the fire, police spokesman Micky Rosenfeld said. He refused to provide further details, but said: "We're talking negligence at the moment."
There have been conflicting reports about what sparked the fire. Israel Radio, citing unidentified police officials, said early Saturday that the blaze likely was started by a family that failed to extinguish a picnic fire. Israeli TV, meanwhile, has reported that kids holding a bonfire may have been the source.
The blaze, which broke out Thursday, tore through the hilly pine Carmel Forest that clings to the mountain ridge above the northern city of Haifa, Israel's third-largest city. It also lapped at the edges of small outlying communities.
The fire has killed 41 people - most of them prison guards whose bus was engulfed by flames as they rushed to evacuate a prison. A 16-year-old volunteer firefighter also died after joining the rescue mission.
More than 17,000 people had been evacuated from their homes before officials gave some of them the all-clear to return on Saturday. Firefighter spokesman Yoram Levy said the blaze had subsided, but added that he "can't say it's under control."
Critics contrasted Israel's helplessness in the face of a wildfire with its reputation for swift and effective responses to disasters abroad.
"We are experts in some tragedies but it seems we were not really prepared for an event related to fire," said Hanan Goder, a spokesman for the Foreign Ministry, which is helping to coordinate the international response to the fire.
Israeli firefighters have complained for years of undersized crews, outdated equipment and minimal supplies. The country only has 1,400 firefighters, far below the worldwide average. And while it has a highly sophisticated air force, it doesn't have a single firefighting plane. It ran out of flame retardants on the first day of the blaze, Levy said.
In the small artist community of Ein Hod, one woman desperately tried to protect her house from the encroaching flames with only a garden hose.
Netanyahu told a news conference Saturday evening that his government would find the money to form an airborne firefighting force.
International aid continued to flow into Israel in a bid to help quell the fire, which continued Saturday to rage out of control for a third day.
U.S. planes laden with equipment were expected to land later Saturday, alongside aircraft sent from New York City's firefighting department, an Israeli military official said. French and Italian firefighting planes were also en route.
The aircraft are expected to join firefighters and planes that already have arrived from Bulgaria, Greece, Jordan, Turkey, Russia, Cyprus and Britain. Aid has also come from Egypt, Jordan and the Palestinians.
Netanyahu sought to stress that one important thing has emerged from the crisis.
"Israel stands united, and many states stand by Israel's side," said Netanyahu, whose government is embattled over stalled Israeli-Palestinian peacemaking.
By Saturday, the fire had burnt some 15 square miles (40 square kilometers) of land - more than one-third of the Carmel Forest, parks officials said.
While small by international standards, the loss of the verdant forest land was keenly felt in Israel, where only 7 percent of the land is wooded. The Carmel forest makes up 5 percent of that forested land.