A police constable has been arrested from Tinsukia district of Assam in connection with the abduction of ONGC employees.

Assam director-general of police B.J. Mahanta in a series of tweets on Monday evening said Basanta Buragohain, a constable of the 25 AP (ONGC) Battalion, was arrested for “actively participating” in the abduction of the three ONGC employees from a rig site at Lakwa in Upper Assam’s Sivasagar district on April 21.

The constable was “part of the entire conspiracy” along with two other “bad characters” apart from the Ulfa (I) leaders, he said.

Buragohain had not reported for duty since April 21, the day of the abduction, fuelling suspicion about his role in the case.

Two of the three ONGC employees — Alakesh Saikia ( Jorhat) and Mohini Mohan Gogoi (Sivasagar) — were rescued from Mon district bordering Myanmar on Thursday night in a joint operation by the army, Assam Rifles and Nagaland police personnel.

“Investigation indicates involvement of only 1 police personnel so far but anyone found directly or indirectly involved in this case will be seriously dealt with as per law. All relevant facts are bound to come out on debriefing of the apprehended Basanta Buragohain,” Mahanta tweeted.

Efforts are on to trace out and rescue the third victim — Ritil Saikia of Golaghat district — from Ulfa (I) custody, he added.

Mahanta’s first tweet on Monday had said three persons have been arrested for being “directly involved” with the abduction case in addition to some others linked with the banned outfit.

The other two arrested accused are Biraj Chetia of Dibrugarh, who had purchased the motorcycle used in the abduction, and Rahul Mohan of Sivasagar district for “rendering logistical support” in ferrying the motorcycle to the site and providing other assistance.

Buragohain hails from Chapakhowa in Tinsukia district but was posted in Lakwa.

The number of people arrested in the case has gone up to 17, including 14 arrested earlier from in and around Lakwa by Sivasagar police for their links with the proscribed Ulfa (I).

The abducted trio were whisked away in an ambulance stationed at the rig site towards the Nagaland border. The vehicle was found abandoned near the Nimonagarh jungle “close” to the Assam-Nagaland border.

Security has been tightened at Oil India Limited and ONGC sites in Upper Assam following the incident, moreso after Ulfa (I) in a statement on Friday blamed the ONGC for all the developments while threatening the energy major of dire consequences in thefuture.

The outfit also said it had handed over the three abducted ONGC employees to villagers of Tokoksinghu in Mon district after they were confronted by security personnel, adding that around 500 personnel of the army, Assam Rifles and Nagaland police had launched the search operation at 10pm on Thursday and continued till 2.30am.