A spokesman for Israel's fire department says it's investigating the cause of a blaze at the Jerusalem offices of an Israeli rights group the previous night.

Spokesman Yoram Levy said Monday the fire erupted on the floor of a building where B'Tselem's offices are located. He says extensive damage was caused to the group's offices. Other offices were also damaged.

B'Tselem says its office was empty. Police said one person in the building was slightly injured.

Sunday's ire came amid what B'Tselem and other dovish groups say is an atmosphere of incitement fostered by hard-line legislators and activists against the rights groups. Hawkish non-governmental group Im Tirtzu recently released a video accusing the heads of some dovish groups of undermining the country because their organizations receive foreign funding.