The Guwahati refinery Tuesday escaped a disaster after a bomb was detected near its outer boundary wall.
Assam's Inspector General of Police S.N. Singh said investigation was on to find out who could have planted the bomb in the high-security area.
"The bomb is hand-made and not very powerful," he said.
The refinery is located about 100 meters from the Noonmati police station. The bomb was spotted by some locals who alerted the police.
Meanwhile, two people including a policeman were injured after a youth lobbed a grenade at Jorhat town in Upper Assam Tuesday.
While escaping on his cycle, the attacker dropped some ammunition and two more grenades.
Singh linked the youth to the anti-talk faction of the United Liberation Front of Asom (ULFA).