The police arrested two persons, allegedly cadres of ULFA and recovered explosive material in huge quantity from them in connection with the grenade blast outside a mall on Zoo Road in Guwahati on Wednesday.
In the grenade blast took place at 8 pm on Wednesday, 12 people were injured.
The police recovered explosive materials, pistol and bullets from the two arrested persons, said Deepak Kumar, Guwahati Commissioner of Police.
"We had received credible information that there are three-four people staying at a house in Panjabari who are behind this blast. When we raided the house, we arrested one man and a woman. They belong to ULFA. We have also recovered 20 kg of gun powder, one 9 mm pistol and 25 rounds of active bullets," he added.
He added that the investigation is still on.
The police earlier said that two unknown bike-borne suspects lobbed a grenade on state police troops and fled the spot.
The area was later cordoned off the injured were referred to Guwahati Medical College Hospital for treatment.