"We have issued a lookout notice against Narayan Sai, son of Asaram," Surat Police Commissioner Rakesh Asthana said.
"We have informed immigration authorities that a grave offence has been registered against him. This (lookout notice) is a precautionary step so that he cannot leave the country," Asthana said.
Fresh sexual assault complaints were registered yesterday against controversial Asaram and his son here after two sisters accused the duo of abusing them.
They also damaged vehicles, including a bus, two cars and some motorcycles, parked outside the ashram.
As the police arrived to control the mob, most of them fled from the scene, the ACP said, adding the situation is under control.
In Surat, Asthana said police teams have started investigation in the case and Sai is being traced. He said they have identified a few locations where he could be.
Asaram, 72, was arrested in August on charges of sexually assaulting a minor girl and has been in prison at Jodhpur in Rajasthan since then.
Police registered two complaints - one against Asaram and another against Sai - of rape, sexual assault, illegal confinement and other charges.
The complaint against Sai was registered at Jhangirpura Police Station in Surat, while the one against his father Asaram was transferred to Ahmedabad as the alleged incident happened there.
The elder sister in her complaint accused Asaram of repeated sexual assault between 1997 and 2006, during the time she had been living in his ashram on the outskirts of Ahmedabad city.