A pipe bomb exploded outside a synagogue in Santa Monica, Los Angeles on Thursday, but there was no immediate report of injuries or damage, police said.

The explosion took place about 6:45 a.m. in the parking lot of the synagogue, prompting police to evacuate a four-block area, authorities said.

Police did not say whether the explosion was an act of terrorism, but said an investigation has been launched into the possibility of a hate crime.

Authorities said they were trying to determine whether the synagogue was specifically targeted.

The Los Angeles Police Department sent a bomb squad to the scene.

The FBI and Santa Monica Police both were assisting the investigation, sources said.