Nagarkurnool/Thiruvananthapuram | Cadaver dogs of Kerala police on Thursday arrived in Telangana's Nagarkurnool to join the rescue operation at the partially collapsed SLBC tunnel in which eight persons remain trapped since February 22.

The dogs arrived by air and their handlers went inside the tunnel along with officials.

A plan will be prepared on how and where to take the dogs to look for human presence and the canines would be taken inside the tunnel on Friday morning, an official release of Telangana government said.

Cadaver dogs are specially trained to locate missing humans and human bodies. The canines and the officers handling them left for Hyderabad on Thursday morning, a Kerala government statement said in Thiruvananthapuram.

The dogs were sent for the rescue operation following a request by the State Disaster Management Authority whose help in the matter was sought by the National Disaster Management Authority, the statement said.

The rescue personnel had earlier used the services of a sniffer dog of the NDRF inside the tunnel for selecting the area to be taken up for digging to identify any human presence.

The Telangana government release said Col Kirti Pratap Singh, a senior official of the National Disaster Management Authority (NDMA) visited the tunnel site on Thursday.

The state government's Special Chief Secretary (Disaster Management) Arvind Kumar briefed Singh about the ongoing rescue operation.

The release said the 150 metre-long Tunnel Boring Machine (TBM) was completely destroyed in the accident at 13.650 km inside the tunnel after stones and debris fell on it. Soil, water and stones got deposited at the place.

The eight persons are suspected to have got trapped there, it said.

Efforts are being made to locate the trapped men by cutting down the huge TBM.

The release further said the conveyor belt at the tunnel has been made operational and the rescue operation would gain speed after soil can be sent out using the belt.

The conveyor belt got damaged after the accident.

The rescue officials have already carried out digging for human presence at the locations suggested by the scientists of National Geophysical Research Institute (NGRI) in Hyderabad but it has not yielded results so far.

The scientists deployed a Ground Penetrating Radar (GPA) to identify any "anomalies" inside the tunnel.

However, water and slush inside the tunnel posed a challenge to the rescue personnel.

Eight persons -- engineers and labourers -- have been trapped in the Srisailam Left Bank Canal (SLBC) project tunnel since February 22 and experts from the NDRF, Indian Army, Navy and other agencies are making relentless efforts to pull them out to safety.