Jerusalem (CNN) -- Five U.S. Defense Department aircraft will leave for Israel this weekend to help fight a wildfire that has killed at least 41 people and injured 17.
They include three C-130 fire-fighting aircraft from the U.S. Air Force Reserve and Air National Guard and two C-130s from the U.S. European Command, which will depart Ramstein Air Base in Germany carrying 20 tons of fire retardant, the U.S. Agency for International Development said.
The agency said it has already chartered commercial aircraft to deliver 45 tons of fire retardant and 12,000 liters of foam to suppress the flames.
A team of experts from the U.S. Forest Service's Disaster Assistance Support Program is also heading to Israel, the agency said.
Israeli police said Friday they suspect arson in the wildfire, which has burned more than 7,400 acres in the past three days and is the worst in the nation's history.
British Prime Minister David Cameron instructed the Royal Air Force to deploy two helicopters from Cyprus to help put out the fire, British Foreign Secretary William Hague said Friday.
Hague expressed his condolences to the families of the victims and to the thousands who have had to be evacuated because of the blaze.
"This tragedy is all the more sad as it comes as the Jewish community around the world celebrates Hanukkah, a time of hope and joy," Hague said. "The UK will continue to do whatever it can to help."
Israeli Prime Minister Benjamin Netanyahu spoke Saturday morning with the president of Switzerland to recruit additional air support, his office said.
A police investigative team and a fire expert team have been working to determine the cause of the fire, which started from a single location, said Dudi Cohen, Israeli police commissioner.
Forty of the fatalities were cadets in Israel's prison service who were en route Thursday to help evacuate 500 inmates from Damon prison near Haifa when their bus became engulfed in the fast-moving blaze, the Jerusalem Post reported.
Israeli firefighter spokesman Yoram Levy said shifting 29 kph (18 mph) winds made the inferno harder to control as flames neared a neighborhood in Haifa, a major tourist destination on the northern coast.
Built on the slopes of Mount Carmel about 50 miles north of Tel Aviv, Haifa's metropolitan area is also host to historical sites that date to Biblical times.
More than 15,000 people have been evacuated from villages and towns in the area, emergency officials said.
The fire has also threatened a sensitive ecological area near the Hai Bar nature reserve. Known as Mount Carmel's "Little Switzerland," the reserve is home to a wildlife preservation project that seeks to bring back native species mentioned in the Old Testament.
The fire has triggered an outcry in Israel. Though the nation is known for its military might, it has failed to handle the calamity, according to critics.
Netanyahu acknowledged Friday during a Security Cabinet briefing that Israel could not cope with the wildfire alone and thanked the more than 13 nations sending emergency crews and equipment to help douse the blaze.
In addition to the United States and Britain, Russia, Greece, Cyprus, and Turkey have also sent aid.
Relations between Turkey and Israel have been tense since last spring, when Israeli commandos boarded a Turkish ship carrying humanitarian aid for Gaza, killing nine people. Netanyahu called Turkey's help a "very blessed step" and promised to show Israel's appreciation.
