Witnesses said they saw vehicles flung into the air by the force of the explosions -- one car was found on the roof of a three-story building.
Zong Han-Li was driving when the explosion happened directly in front of him, and his dashboard camera caught the moment the gas ignited.
"The explosion left a trench two meters deep. Some vehicles were blasted into the air, and some people fell into the trench. It was a devastating scene."
"It was very loud when the explosion happened, (and) debris was blasted into the sky. Motorcycles were tossed as high as three stories. Everyone came out to help because there were already injuries."
Two people were blown to the roof of a four-story building, where emergency workers found them and took them to the hospital for treatment, CNA reported.
Firefighters from neighboring cities rushed to Kaohsiung to help battle several fires, which had been mostly contained by Friday morning.
At least 25 people were killed, including four firefighters. Twenty-two emergency workers were among 267 people injured, officials said. A number of people were still missing, including a senior fire official who went to investigate reports of a gas leak.
As daylight broke the extent of the damage became clear, with wrecked cars and motorcycles strewn across the cratered streets.
Dave Flynn, an English expatriate who has lived in the city for several years, visited the site of the explosions Friday morning. He told CNN that a huge trench had been gouged along the length of a main thoroughfare for several kilometers, and the pavement had been thrown to the side of the road, damaging vehicles.
"There were police cordons on the major intersections but they were just stopping vehicles," he said. "Most of the side streets, you could just walk into the area and it was full of pedestrians checking out what had happened. I saw people fixing their own houses, and I saw the army arrive, some trucks to clean up some of the (wrecked) cars."
Schools and offices in the Cianjhen district, as well as the neighboring Lingya District, were closed on Friday to facilitate rescue efforts, Mayor Chen Chu told reporters. Several schools and a cultural center are being used as emergency shelters.
Authorities suspect ethylene, propane or butane in the explosions. There are several petrochemical factories in the region.
The government called up hundreds of soldiers to assist in search and rescue efforts.