Taiwanese authorities are investigating LCY Chemical Corp., the Taipei-based petrochemicals firm that made the pipes that burst in Thursday night's deadly gas-pipeline explosions in Kaohsiung.

The LCY-built pipelines were reportedly leaking nearly four tons of propene every hour starting at 8:45 p.m. local time, which eventually caused deadly blasts in the underground networks of Kaohsiung that killed 27 and injured 267. The series of explosions took place three hours after authorities reported the gas leak but could not determine its origin point.

"The leak was very far from the explosions, because propene was leaking and spreading through the sewer system everywhere," Chen Chin-der, director of the Environmental Protection Bureau in Kaohsiung, said, according to the Associated Press, adding: "When the density of propene is very high, anything can trigger an explosion, anything as small as a cigarette, or starting the engine of a motor scooter."

LCY said it will cooperate with the investigation.

“Our priority is to figure out the truth and responsibility," said Pan Lee-lin, a company spokesperson, according to AP.

While residents in the region questioned authorities on why they couldn’t find the source of the leak before the blasts happened, government officials investigating the case let evacuated locals return to their homes late Friday.

"It dragged on too long because they couldn't identify the source," a resident told a local television network, according to AP, adding that just minutes before the explosion, the authorities reportedly said, “Everything is under control. You can go home and sleep.”

Such pipelines run throughout the area, and the explosions were the worst the country has seen in 16 years, AP reported.

"I instructed relevant units to thoroughly inspect the pipelines and call for the central government to review how to properly locate them so residents do not live under invisible threats and to prevent another tragedy," Chen Chu, Kaohsiung’s mayor, said in a statement, according to BBC, noting the explosions have “shocked residents tremendously.”