"The senior most additional district magistrate M K Marak was asked to probe the incident and was given 30 days time to submit the report," East Garo Hills district Deputy Commissioner Vijay Kumar Mantri said.
He said, "The magistrate would also see how these gunmen could penetrate the gates of the jail."
Heavy armed militants on Saturday attacked the Williamnagar district jail leading to the killing of Assistant Jailor Neil Nongkynrih and jail warden Sarai Singh Thabah.
The district authorities have established that the jail attack was by ANVC (B) and not GNLA as was initially suspected, official sources said.
However, both ANVC-B and GNLA denied any role in the attack.
Director General of Police Kulbir Khrishan had admitted security lapse for the mishap and said it was a targeted killing and not an attempt to break the jail.