grenade caused a fire at an oil distribution terminal operated by Thai Petroleum Pipeline Co., an affiliate of PTT, on Tuesday night but it was brought under control, Thai energy minister Wannarat Chanukul said.

“Attackers threw two M79 grenades. One of them didn’t go off. The affected tank is a jet fuel tank supplying Suvarnabhumi airport,” Wannarat told reporters on Wednesday, referring to Bangkok’s main international airport.

Officials took an hour to control the fire outside a jet fuel tank at Lumlukka terminal in Pathumthani province, north of Bangkok, the company said in a statement, adding there had been no injuries and no disruption to its services.

Officials did not know who threw the grenades, or whether the incident was linked to political unrest in Thailand over the past six weeks during which several grenade attacks have been reported.

Thai Petroleum Pipeline has 19 oil tanks with 20 million litres each at Lumlukka terminal, most of them supplying Suvarnabhumi airport.

Top energy firm PTT owns 33.2% of the company and other major shareholders include Thai Oil, Esso (Thailand), Thai units of Shell, Chevron, Kuwait Petroleum, Petronas and BP.