Firemen who spent two hours fighting a huge blaze at an industrial centre in Tsing Yi on Tuesday night found 750 litres of dangerous chemicals, allegedly stored illegally, and a number of unauthorised structures. They found 26 drums of bleach and four drums of acetic acid, each containing 25 litres, after breaking into a second-floor unit. Man Shu-bor, acting senior divisional officer of the Fire Services Department's southwest division, said: 'Initial investigations show that the dangerous goods were kept in the unit without a licence. 'Samples have been sent to a government laboratory for examination. If we confirm the solutions are dangerous goods, we will take legal action.' Acetic acid is classified as Category No3 dangerous goods. Fifty litres can be stored without a licence. For bleach, a Category No4 dangerous good, 250 litres can be stored without a licence. The blaze broke out in an illegal structure on the second-floor podium of the Cheung Tat Road building at 9.48pm on Tuesday. Firemen said it was used to store second-hand goods, such as computer monitors, air conditioners, refrigerators and furniture. It was upgraded to a No3 alarm at 10.16pm and then a No4 alarm at 10.43pm as it spread to another illegal structure and two units on the same floor and two more units on the third and fourth floors. Twenty-two engines and two ambulances were despatched. About 120 firefighters finally extinguished the blaze at 12.08am yesterday. A fireman who fell ill after inhaling smoke was treated at the scene and did not need hospital treatment. Firemen are investigating the cause of the blaze, but the department said nothing suspicious had been found. The Buildings Department said the owners of the two illegal structures which were damaged in the blaze have been ordered to demolish them. A spokeswoman said: 'If they fail to comply, they will be prosecuted. There are more than 10 other illegal structures on the podium. We are following up.'