Firefighters Inadvertently Cause Spill : Emergency: As a crew fought a trash-truck blaze in Orange, they noticed a caustic substance leaking.

An attempt by firefighters to put out a fire in a trash truck Friday morning inadvertently caused a chemical spill that forced the closure of a street and the evacuation of two industrial buildings, fire officials said.

Officials have not been able to determine the composition of the highly caustic chemical, which ate a hole into the steel floor of the trash truck and in a chunk of asphalt, Orange Fire Battalion Chief Ray Montoya said.

“This has been a real strange one,” Montoya said. “We weren’t sure what to make of it. It just kept getting bigger and bigger. Very unusual.”

The bizarre incident began about 7 a.m. when a fire was reported inside an Orange Disposal truck picking up trash in the 600 block of West Collins Avenue.

“It came in as a routine trash truck fire, which we get all the time,” Orange Fire Battalion Chief Dick Dittberner said. “But when the arriving engine started putting out the fire, they noticed that something was dripping out of the truck that was not water and it was solidifying as it reached the ground.”

The firefighters stopped dousing the flames with water when the runoff carried about 200 gallons of the chemical into storm drains in the 800 block of Batavia Street. A hazardous-materials team from the Anaheim Fire Department was called to the scene to clean up the chemical.

There were no injuries. It took 20 firefighters more than seven hours to extinguish the blaze, which was confined to the inside of the back of the garbage-filled truck, Dittberner said.

As a precaution, about 50 workers from two industrial buildings were evacuated for most of the day, and West Collins Avenue was closed from Main Street to Batavia Avenue.

Dittberner speculated that someone may have illegally placed containers of the chemicals inside a trash bin. When the bin was dumped into the truck, it may have combined with other materials and caught fire.

The fire burned through some fuel lines in the trash truck and caused its hydraulic system to fail, so that firefighters could not open the back of it to get to its contents.

The blaze was finally extinguished just before 3 p.m. after firefighters used a backhoe to open the truck. The trash truck driver had finished his route, so the truck was filled with “a tremendous amount of trash,” Dittberner said.