Chandigarh, Jan 25: Authorities have discovered another tunnel inside the Burail Jail from where four undertrials, including three accused in the Beant Singh assassination case, escaped a few days ago. Jail sources say the tunnel was found inside barrack number four where another four accused in the Beant Singh case are lodged. The four are Lakhwinder Singh alias Lakha, Nasib Singh, Shamsher Singh and Navjot Singh.

The tunnel has been filled with mud so it's difficult to ascertain its exact measurement. Roughly, it has been dug about 6-7 feet vertically and 10-15 feet horizontally, sources said. The new tunnel heads towards barrack number seven, that housed the four escapees.

Meanwhile, after interrogating the arrested jail staff, the police has ruled out negligence and is seriously suspecting their connivance.

There is evidence that prison staff at various levels had information that digging was going on inside the jail. "It is likely that money exchanged hands so that they did not interfere," an investigating officer said.

The jail staff is also suspected to have hidden evidence from the police.

Several agencies including RAW, CBI and the Intelligence Bureau are in Chandigarh, questioning different officials in connection with the case.