The business held £159 million ($270.56 million) of stock as of May 31 of which around 70 percent is held at Barnsley.
Asos said it was "fully insured for loss of stock and business interruption".
South Yorkshire Police are treating the incident as "deliberate" and have launched a criminal investigation.
"It has come at quite a bad time because they have had a couple of bad months. They had to announce a profit warning so it's bad timing for them," Anusha Couttigane, fashion consultant at Conlumino, told CNBC in a phone interview.
Asos has had a challenging year, Read Moreissuing its second profit warning in three months at the start of June. The company reduced its operating margin guidance to 4.5 percent from 6.5 percent for the current financial year.
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Nick Robertson, CEO of Asos, said the profit for the three months ending May 31 was "not what we had hoped for", citing a strong pound.
Shares in Asos were caught up in the momentum stock sell-off earlier in the year, in which investors fell out of love with the bubbly technology sector. Asos shares are down 55.7 percent this year.
It is not the first time that an Asos warehouse has suffered damage. In 2005, the company's Hemel Hempstead distribution center was damaged by explosions at a nearby oil depot.