A group of Israeli settlers broke into an all girls' school in the Nablus districton Wednesday, setting fire to its storehouse containing furniture and unused sports equipment, the headmistress said.

Maysoon Sawalha said the cleaning woman at the school in As-Sawiya village arrived to find the lock on the main door broken as well as that of the storehouse, and all its contents were torched.

The fire did not spread to the rest of school because the water main is located in the storehouse, she said, adding that "otherwise the whole school would have been set on fire."

Settlers wrote racist slogans on the school's walls, including "regards from the hilltops," she added.

"This is not the first attack on the school. Many attacks were carried out previously, the last of which was last year when settlers intercepted one of the classrooms and fired rounds of ammunition and gas canisters," Sawalha said.

An Israeli military spokeswoman said a complaint had been filed with Israel's Civil Administration, and the body was in touch with Palestinian Authority officials to "keep things quiet" in the area.

Israeli police, she added, are investigating the incident.

Sawalha called on international organizations to work on stopping such attacks "that put the life of the girls at risk causing them to suffer psychologically."

An Israeli settler leader told Ma'an that there was scant evidence implicating any particular party, and added that tensions were high due to visits by activists helping local Palestinians harvest olives.

"Yes, Jews might have lit the fire, but it also could have been delinquent Arab youth from As-Sawiya or demented provocateurs like [Rabbis for Human Rights director] Arik Ascherman who was seen in the same area yesterday trying to ignite tensions between local Arabs and Jews," said David Ha'ivri, director of the Shomron Liaison Office.

"Every year as the olive harvest arrives the region is overrun with outsiders claiming to be 'peace activists' or 'humanitarian aid givers' who wish to take part in the action and when they find nothing newsworthy going on they volunteer to make things more exciting by initiating violent events," he said in an emailed statement.

On Tuesday, an Israeli rights group reported that 90 percent of claims filed against settlers in the West Bank for assault to person or property against Palestinians fail to secure a conviction.

Responding to that report, Ha'ivri said, "Could it be that 90% of the complaints filed do not lead to conviction of local Jewish residents be due to the fact that there is no evidence to back up those suspicions?"

Wednesday's suspected arson follows a wave of reports from Palestinian farmers that settlers have been setting fire to agricultural land since the beginning of the traditional olive harvest in October.

In early October, Israeli settlers were suspected of setting fire to a Bethlehem village mosque.

Director of PA Ministry of Religious Endowment in Bethlehem Muhammad Ayish at the time described the arson as a "campaign against everything Palestinian."