TAIPEI (AFP) -- The head of the company allegedly responsible for deadly explosions that rocked Taiwan's second city apologised on Sunday, as authorities said the firm failed to notify them quickly enough of a gas leak blamed for the blasts.

"Regarding the Kaohsiung explosion, I would like to make an apology to the public on behalf of the company," Bowei Lee, CEO and chairman of LCY Chemical Corp, told reporters with a deep bow of respect.

The blasts sparked massive fires which tore through the city of Kaohsiung's Cianjhen district late Thursday, killing at least 28 people and injuring more than 300.

"We'll by no means shirk responsibility if any is confirmed, nor have we concealed anything," he added. "We want to know the cause more than anyone."

The powerful gas explosions -- the worst in Taiwan's history -- shattered thousands of windows and left doors twisted in their frames, while vehicles were thrown onto the roofs of buildings several stories high.

The company, which distributes propene gas through its pipe network beneath the city, has argued that there was not a leak in its system.

Lee declined to provide more details of what happened on the night of the incident.

The Kaohsiung city government has insisted that LCY Chemical was the sole company transporting dozens of tonnes of propene through the pipelines, backed up by documents seized from the company.

"The casualties could have been less serious should the company have reported the leak to the authorities and taken emergency measures after it happened," said Chen Chin-teh, chief of environmental protection bureau in the city government.

He estimated that more than 10 tonnes of propene might had been leaked in the hours before the first explosion.

President Ma Ying-jeou, who visited a Kaohsiung hospital where the injured were recuperating on Saturday, has vowed a full investigation into the cause of the incident, and a review of the pipe network.

Kaohsiung lies adjacent to a huge petrochemical complex housing dozens of plants and many pipelines run under the densely packed city.