At least 18 people from Assam's Tinsukia district have been killed and three others are missing after the truck they were travelling in fell into a gorge in Arunachal Pradesh, officials said on Thursday.

The incident occurred on Hayuliang Chaglagam Road in Anjaw district earlier this week, Tinsukia District Commissioner Swapneel Paul told PTI.

He said that around 11 am on Thursday, authorities received information that a vehicle had fallen into a gorge in the remote district.

The news of the accident became public only after the lone survivor reached a nearby Army camp on Wednesday night and informed the authorities.

“Accordingly, we contacted the DCs of Anjaw and Teju for confirmation,” he added.

Assam chief minister Himanta Biswa Sarma on Thursday expressed his condolences over the deaths, and said both states were working closely to locate the people who have been missing.

Sarma said that he is deeply pained by the passing away of the people from Assam in the accident.

"Our district administration is in touch with relevant authorities in Arunachal Pradesh and all necessary assistance is being provided," he said in a post on X.

Sarma said relief and rescue teams are prioritising locating missing people.

"We are also ensuring that medical help is provided to those in need. My thoughts and prayers are with the grieving families in this tough time," he said in the post, tagging Arunachal Pradesh CM Pema Khandu.

The Chief Minister's Office in a separate post said the Tinsukia district administration is coordinating closely with Arunachal Pradesh authorities, as teams work through harsh terrain for rescue and relief efforts.

"Essential arrangements are underway to provide relief and medical support to those affected," it said.

A team from Tinsukia, including a circle officer and police personnel, has been sent to the neighbouring state to gather further updates.

“They have reached Tezu and within 2 to 3 hours, we will be able to give more details,” he said.

Tinsukia Circle Officer Jaideep Rajak, who is on the way to the site, told PTI that the location is remote and the exact details will be known only after reaching the spot.

“Initial reports indicated that the workers were engaged by a private contractor in a project in Hayuliang. They were travelling in a dumper that skidded off the road and fell nearly 1,000 feet into a deep gorge. Rescue operations are underway,” he said.

Tinsukia Senior Superintendent of Police Mayank Kumar said that 22 labourers from the district had gone to Arunachal Pradesh for the construction of a hostel.

“They were from Dhelaghat of Gillapukri Tea Estate. Out of the 22 people in the dumper, 21 are reportedly dead,” he said.

One of the workers, Budheswor Deep, managed to escape and alerted his relatives on Wednesday morning, which first informed families of the incident, Kumar said.

Apart from Deep, 18 more labourers including those dead and missing have been identified.

They are Rahul Kumar, Somir Deep, Arjun Kumar, Pankaj Manki, Ajay Manki, Bijay Kumar, Abhoy Bhumij, Rohit Manki, Birendra Kumar, Agor Tanti, Dhiren Chatriya, Rojoni Nag, Deep Gowala, Ramsebak Suna, Sonaton Nag, Sanjay Kumar, Karan Kumar and Junash Munda.