The fire that destroyed a portable classroom Sunday at Wilcox Elementary School was caused by an electrical problem, fire investigators said.

They concluded that the fire was "not of suspicious origin" and identified the source of the blaze as an electrical outlet or the television/VCR unit that was plugged into it.

The portable classroom, more than 20 years old, had been used by one of Wilcox's special-education classes.

Kaua'i schools superintendent Danny Hamada said the school had concluded there was no asbestos in the structure, but tests were still being performed to determine whether the paint on the wooden structure contained lead.