HAIFA: European aircraft dumped tons of water over flames raging through tall trees in northern Israel as firefighters struggled for a second day Friday to contain the country's worst-ever forest fire, which has killed 41 people and displaced thousands.

Authorities raised the possibility of arson, saying several small fires that broke out in the same general area but were quickly contained appeared to have been deliberately set.

But the cause of the main fire, whipped by strong winds through one of Israel's few natural forests, remained unclear. Public Security Minister Yitzhak Aharonovich told Channel 2 TV that if the big blaze did turn out to have several distinct centers, ''then it would look like arson.''

But police chief David Cohen said later at a news conference that the fire broke out in a single center and could have been caused by carelessness. Two Druze men arrested on suspicion they planned to set a smaller fire were cleared and released, Cohen said.

Flames nearly 100 feet (30 meters) high spread across a hilly pine forest toward the Mediterranean Sea, as the blaze reached the outskirts of Israel's third largest city, Haifa.

Helicopters and planes flew back and forth to the Mediterranean, scooping up sea water and dumping it on the fire. Turkish planes scattered white powdery material over the smoky hills. Banana trees were burned and cypress trees were stripped of their leaves with only thin trunks remaining.

One of the main country's highways was closed to traffic as nearby trees smoldered and smoke billowed toward the Mediterranean coastline, with ash flying through the air and large red flames closing in on a hotel and a spa south of the city.

The eruption of the blaze Thursday overwhelmed Israel's small firefighting force and prompted an unprecedented call for international help from a country better known for sending its own rescue teams and medical personnel to other countries' disaster zones.

Yoram Levy, a spokesman for Israel's fire and rescue service, said the fire was huge and that firefighters battling strong winds were having trouble accessing the mountains and valleys.

''We don't have big aircraft that can carry a large amount of water,'' Levy said. ''It is not enough for a large-scale fire.''

The US was sending a team of firefighting experts and large amounts of fire-retardant chemicals to Israel over the weekend, and is trying to fulfill the Israeli request for aircraft, Obama administration officials said Friday.

President Barack Obama expressed his condolences for the loss of life to Israeli Prime Minister Benjamin Netanyahu during a telephone call from Air Force One after it departed from Afghanistan. Obama had made an unannounced holiday visit to U.S. troops there.

Some 100 firefighters from Bulgaria arrived as well as fire extinguishing planes and crews from Greece and Britain, Israeli officials said. More aid was on its way from Russia, Egypt, Cyprus, Jordan, Spain, Azerbaijan, and Romania.

Turkey set aside tensions over Israel's deadly raid on a Turkish Gaza-bound flotilla in May to lend a hand _ though Turkish Prime Minister Recep Tayyip Ergodan underlined that the help didn't mean ties were back to normal and said his country still wanted an apology for the raid and compensation for the victims.

Still, Netanyahu singled out Turkey for thanks as he expressed his appreciation to countries around the world for their help.

''We are amid a disaster of international proportions,'' he said after an emergency Cabinet meeting to discuss the fire. ''We have to admit that our firefighting services cannot handle a forest fire backed by such a strong wind. We don't have the means for it.'' Netanyahu then headed north to visit the injured in hospitals and inspect firefighting efforts.

Foreign Minister Avigdor Lieberman told Israel Radio that he was hopeful the fire could be suppressed by Saturday night.

Defense Minister Ehud Barak ordered the military to make all its resources available for the effort, which was being coordinated by the Israeli air force. The military said it sent soldiers and equipment, including helicopters, bulldozers, medics and army units.

The scorched woodland accounted for only 7 square miles (18 square kilometers) of land. But because only 7 percent of Israel's land is forested, this worst forest fire in Israel's history was felt here as a deep national loss.

Some 15,000 people were evacuated from their homes, and Kibbutz Bet Oren, a collective village in the wooded area, suffered significant damage. Several communities and a neighborhood of Haifa, a city of 265,000 people, were evacuated, along with Haifa University at the edge of the stricken Carmel nature preserve.

The area is a favorite spot for camping, hiking and picnics. A nature reserve provides a refuge for dozens of species of wildlife and forest rangers have evacuated animals from the inferno. after its residents were evacuated, witnesses said. – AP