Chen Chin-der (陳金德), the head of Kaohsiung's Environmental Protection Bureau, said that based on the samples collected at the scene, the bureau has established that a major propene leak caused the multiple gas explosions.

It found that the pressure in the LCY Chemical piping system used to channel propene was abnormal starting at around 8 p.m. Thursday night and that 3.77 metric tons of the gas leaked between 8 and 9 p.m. alone, Chen said.

The company did not shut down the pipe system until 11:40 p.m., the official said, and the first explosion occurred roughly 16 minutes later.

The concentration of propene at the site of the blasts was an abnormally high 13,000 ppm, and could have been set off in the tight confines of the underground piping network by the slightest spark.

A spokesperson for LCY Chemical said earlier Friday that the explosions could not have been caused by the company's piping system for a number of reasons.

He said propene is an odorless gas but the affected residents described smelling a gas odor in the hours leading up to the blasts.

Also, the distance between the company's underground pipes and the locations of the explosions were 10 meters apart, and the pipe it used was only four inches in diameter while the one that burst had a diameter of eight inches.

State-run oil company CPC Corp., Taiwan, which also had gas pipes in the area, said its storage and pumping station in Cianjhen District, the epicenter of the explosions, has three underground pipes, with one of them providing ethylene to its Kaohsiung refinery.

“Initial checks on the pipeline to the Kaohsiung refinery were normal,” said CPC Corp. Vice President Chang Ray-chung.

The other two pipelines, Chang said, supply propene to privately run China Petrochemical Development Corp. and LCY Chemical, and the piping is the responsibility of the two companies.

According to Kaohsiung environmental officials, the two pipelines running between CPC Corp. and the other two companies were idle when the blasts occurred.

But LCY Chemical was bringing in propene through a pipe connecting it to another storage facility in the hours leading up to the explosions, they said.