PALU, INDONESIA (BNO NEWS), Aug 23 -- At least one person was shot dead on Monday after riots broke out on the northern Indonesian island of Tiaka, officials said on Tuesday.

The riots began on Sunday and intensified on Monday afternoon as angry mobs attacked the Pertamina-Medco E&P Tomori Joint Operating Board offices and facilities, located in the Morowali district on Tiaka Island in Central Sulawesi, local authorities told the Antara news agency.

The riots worsened when hundreds of residents from mainland Mamosalato traveled to the island by motor boats and joined the riots, vandalizing the oil facilities which are jointly managed by Pertamina and Medco. Mobs, using machetes, spears, sickles and Molotov cocktails, also took several Pertamina employees hostage.

In addition, the Antara news agency reported that an oil well on Tiaka island was also attacked with Molotov cocktails, causing it to catch fire.

Sulawesi Police Chief Brigadier General Dewa Parsana confirmed the arrests of 19 people who are being questioned for acting unlawfully, conducting vandalism and holding people hostage. Authorities said they would be transported to the Central Sulawesi Regional Police Headquarters in Palu for further investigation.

Parsana later confirmed the death of at least one rioter while three others were injured. No other details about the incident were immediately released.

Meanwhile, Chief of Morowali Police Resort Adjunct Senior Commissioner Suhirman said the cause of the riots were still unknown as security personnel were trying to restore order in the area and evacuate residents to avoid more casualties.

Tiaka Island is located in the Mamosalato subdistrict of Morowali district and is located on the border area between Morowali and Banggai. State-owned Pertamina and PT Medco E&P Tomori form a consortium that owns the attacked oil well.