Haifa, Israel (CNN) -- Israeli police said Friday that they suspect arson in the wildfire that has killed at least 41 people and injured 17 in northern Israel over the past two days.
Police spokesman Micky Rosenfeld cited "suspicious objects" found Thursday. He did not elaborate.
Officials called the wildfire, which had scorched more than 7,400 acres and continued to burn, the worst in the nation's history.
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.
"The bus had no chance; they tried to escape but were burned alive," a firefighter spokesman told the newspaper. "It was a horrific scene."
Eight funerals were held Friday and several bodies were still being identified, 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, which began Thursday morning on Mount Carmel and spread through nearby areas, 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.
Prime Minister Benjamin 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.
During a visit to victims in a hospital in Haifa, most of which was blanketed in smoke, Netanyahu said Russian planes were the latest addition to the international force aiding Israel.
Russia's ITAR-Tass news agency reported that an II-76 plane capable of holding 42 tons of water, an amphibious BE-200 and an Mi-26 transport helicopter also used for fighting fires were scheduled to fly to Israel.
"On the way here, we flew over Carmel, where we heard and saw the Greek aircraft fighting the fire," Netanyahu said. "I very much appreciate the mobilization of many countries."
Netanyahu talked Friday with U.S. President Barack Obama, who said in a statement that officials from the two nations have been "in near-constant contact since the fires began."
Chemicals to suppress the flames -- including 45 metric tons of fire retardant and 12,000 liters of foam -- will arrive this weekend through the U.S. Agency for International Development, that agency said, with teams of U.S.-based firefighting specialists also on their way.
Additionally, a U.S. military official said that Israel has asked for satellite imagery from the U.S. military, as well as planes to carry water and flame retardants.
Israeli fire crews were also aided by Cyprus, England and Turkey, among others. 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.
"This is a very blessed step that the prime minister of Turkey has decided to take," Netanyahu told reporters about Turkey's help. "I appreciate this much in a time of a humanitarian and ecological crisis. We will find ways to show our appreciation."
CNN's Michal Zippori contributed to this report.