Several Molotov cocktails and other incendiary devices were thrown at a northern New Jersey synagogue early Wednesday, The Associated Press reported.

A fire was ignited in the second-floor bedroom of the rabbi’s residence, the report said. Police are treating the attack both a bias crime and attempted murder.

AP noted that Wednesday’s attack on Congregation Beth El in Rutherford was the fourth bias incident within a month against a Jewish religious institution or center in northern New Jersey. Within the last three weeks, a fire was intentionally set at a synagogue in Paramus and anti-Semitic graffiti was discovered at synagogues in Hackensack and Maywood.

However, Bergen County Prosecutor John Molinelli said there was no evidence yet linking the four incidents, though police haven’t ruled out that they might be connected. Molinelli urged residents to be vigilant, but not afraid.

He told AP Wednesday’s intentionally set early-morning fire was possibly the work of more than one person. The incident occurred at about 4:30 a.m., when incendiary devices were thrown at various parts of the large Victorian-style home that houses Congregation Beth El on its ground floor, and the rabbi’s living quarters on the second level.

The rabbi, his wife, five children and the rabbi’s parents were sleeping when the fire occurred. No one was seriously hurt. Police said the device thrown through the rabbi’s bedroom window did not explode, but ignited, and the rabbi suffered minor burns putting it out.

“The manner in which this heinous crime has been committed has brought our office to really raise consciousness on this,” Molinelli told AP. “This is certainly a hate crime, this is certainly a bias crime, this is aggravated arson, but most importantly, we are now looking on this as an attempted homicide.”

He said there was nothing to suggest that the rabbi had been personally targeted, but added nothing had been ruled out so far as the investigation was continuing.

A wide coalition of law enforcement agencies, including the Newark office of the FBI, is participating in the investigation.

Etzion Neuer of the Anti-Defamation League told AP the League was very concerned that there had been four bias incidents in such a short period of time.

“We view these as part of a deeply troubling continuum that we pray will end now,” he said.

The League has offered a $2,500 award for the arrest and conviction of a suspect.