Palestinians said that Israeli settlers in the occupied West Bank burned about 200 of their olive trees on Sunday and also torched surrounding grazing land.
Settlers denied the allegations.
The alleged attackers were seen heading in the direction of the nearby Elon Moreh settlement after setting fire to the trees on land owned by the Palestinian village of Salem, village council spokesman Adli Ishtayeh said.
He said that the trees were on ground adjoining the settlement and, for reasons of Israeli security, kept off limits to their owners for most of the time. He said that the Israeli army, which polices the area, had been notified.
A military spokesman said no complaint against the settlers had been made and that troops on the scene were treating the incident "as a fire, not arson" after unseasonably hot and dry weather.
Settler spokesman David Haivri said Palestinian farmers themselves had been burning dead wood.
"After checking with local security and leaders of the town of Elon Moreh, no unusual events were recorded today in the area," he said.
"We are not aware of more than some small-scale smoke resulting from farmers burning branches from their own pruning after the harvest."
Since the start of the olive harvest last month, there have been scores of Palestinian complaints about settlers cutting down trees, stealing olives or preventing farmers from harvesting their crops, rights groups and police say.
A senior Israeli intelligence officer acknowledged that there had been acts of violence and vandalism by Jews in the West Bank, noting in particular recent attacks against mosques there.
"We are not happy about the situation connected with Jewish extremists in the West Bank," he told a group of foreign journalists on Sunday, speaking on condition of anonymity.
"It needs big efforts in order to stop this wave of violence. We know who are these people. Hopefully we will be able to stop this wave of violence", he added.