Nagarkurnool (Telangana) | The search operation to locate seven persons trapped inside the partially collapsed SLBC tunnel here continued at a rapid pace for the 21st day on Friday.

The personnel of different organisations involved in the operation went inside the tunnel on Friday morning, taking the necessary equipment with them, an official release said.

Rescue personnel from state-run miner Singareni Collieries along with rat miners have been carrying out excavation at the points which have been identified as possible sites of the missing persons.

The Kerala police's Human Remains Detection Dogs (HRDD) were also taken inside the tunnel to these points on Thursday, while robots of a Hyderabad-based robotics company were also on the job.

The robots can access "dangerous places" (inside the tunnel), which humans cannot reach and can operate with 15 times greater efficiency, official sources have said.

The search operation was going on round the clock, including de-watering.

Teams from Army, NDRF, SDRF, HRDD, Singareni Collieries, the robotics company and others have been actively involved in the mission.

The body of Gurpreet Singh, who worked as a TBM operator, was recovered on March 9. The body was handed over to his family members in Punjab.

Apart from Gurpreet Singh, the seven others still trapped include Manoj Kumar (Uttar Pradesh), Sunny Singh (Jammu & Kashmir), Gurpreet Singh (Punjab), and Sandeep Sahu, Jegta Xess, and Anuj Sahu, all from Jharkhand.

The eight individuals—comprising engineers and labourers—got trapped in the SLBC project tunnel after a portion of it collapsed on February 22