SAN DIEGO -- A fire that destroyed a five-story apartment complex under construction was set by arsonists, fire officials said.

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See Images Of Flames Hear From Fire Officials

Members of the Metro Arson Strike Team held a news conference Tuesday and revealed that the fire was a result of arson and was set using materials already on site, however, they revealed little else.

Officials would not tell reporters what type of materials were used or where the fire originated.

Eco-terrorists have been suspected of starting a fire that caused more than $50 million damage, 10News reported.

A large banner near the fire read, "If You Build It, We Will Burn It -- ELF." The Earth Liberation Front is an eco-terrorist group responsible for numerous construction site fires worldwide.

"The motivation at this particular point appears to be related seems to the banner that was recovered initially, but we are well engaged in an investigation to determine whether or not that does meet the criteria was in fact by somebody with those affiliations," said. Capt. Jeff Carle of the Metro Arson Strike Team.

The 29-year veteran said it's the largest loss he's seen in his career.

The destroyed a 200-unit building and caused a 100-foot-high crane to topple, according to 10News.

The heat from the blaze was so intense that window blinds from inside an apartment complex 500 feet away melted.

Carle also said the contractor has already begun the work of rebuilding the site.