Thousands of Israeli rescuers and firemen backed by fire crews from around the globe battled on Friday to conquer the biggest inferno in Israel's history, which has already killed 41 people.
As high winds drove flames towards the northern port city of Haifa, officials said they had found 41 bodies and that the death toll could rise. Four people were still missing.
Police reported another 17 people injured, including three in serious condition and one listed as critical.
By nightfall on Friday, more than 17,000 people had been evacuated from their homes and the fire had incinerated more than 10,000 acres (4,000 hectares) of land, with flames reaching the southern outskirts of Haifa, Israel's third-largest city.
Chezi Levy, spokesman for the Haifa fire service, said the fire was being brought under control in some areas.
"We are cautiously optimistic," he told army radio. "The fires are dying down everywhere except in the southern front where the flames are still high and remain strong, which is where we are concentrating our efforts."
But Israeli police chief Dudi Cohen said the fire was still a formidable force.
"At this moment it cannot be said that the fire is under control, not yet," he said. "I really hope that the fire will be under control by tomorrow evening but we still have a lot to do."
He said a police investigation had ascertained where the fire began, but its cause was still unclear.
"It started in one place. In the coming hours or tomorrow morning, we will get a professional opinion on whether it was an act of negligence, which apparently it was, or whether it was done on purpose."
Most of those killed were prison guards on board a bus, who had been trying to evacuate inmates from a facility in the forest, officials said.
"The bus tried to turn around and some tried to get away but they were caught by the fire from two different directions," police spokesman Micky Rosenfeld told AFP.
Firefighter Albert Munis described his shock when he arrived at the scene of the inferno. "We just saw black, a lot of black," he told AFP, adding that firefighters were being drafted from across the country.
"Anyone who can hold a hose has been called up to the fire station," he said.
The inferno taxed Israel's meagre firefighting resources, with only 1,500 firefighters available across the entire country, a number considered woefully inadequate for a country of 7.6 million people.
Prime Minister Benjamin Netanyahu said international help was crucial to putting out the blaze.
"Our firefighting measures cannot provide an answer to forest fires of this magnitude, especially in the face of such winds," he told his security cabinet.
Aid poured in, with 16 countries offering various types of assistance.
By Friday afternoon, four Greek planes, a Cypriot plane and helicopter, two British helicopters and two Turkish planes had joined the operation, backed by 92 Bulgarian firemen, the Israeli military said.
"Today and tomorrow, planes and helicopters are due to arrive from the United States, Russia, Spain, Italy, Romania, Switzerland, France, Croatia and Azerbaijan," the foreign ministry said.
Later on Friday, the premier's office said in a statement Netanyahu had also telephoned the leaders of Belgium, Finland, Germany, Norway and The Netherlands to ask them to send more firefighting aircraft as reinforcements.
Firefighters from neighbouring Jordan also joined the operation on the ground, while Palestinian firemen were drafted in to handle fires which broke out in two Arab villages in northern Israel.
Russia was also sending a large firefighting plane and Israel was hoping to hire a "supertanker" aircraft from a US company.
On Friday afternoon, another fire broke out west of Haifa, but it was quickly extinguished and police arrested two people on suspicion of arson, Rosenfeld said.
The cause of the major blaze was a mystery, but a fire service spokesman said it appeared to have started in a rubbish dump in the Druze village of Isfiya, an account supported by witness testimony, the Haaretz daily reported.
Pilot Alon Chaim said he had spotted a small fire outside Isfiya shortly after 11:00 am (0900 GMT) on Thursday.
