This Surrey, B.C., recycling plant had to be evacuated Monday when workers suddenly fell ill.This Surrey, B.C., recycling plant had to be evacuated Monday when workers suddenly fell ill. (CBC)

A recycling plant in Surrey, B.C., is in lockdown after an unknown gas suddenly filled the facility early Monday, causing eight workers to fall ill.

Firefighters and a hazardous materials team were called in about 8:30 a.m. PT when workers in the Wastech plant on 192 Street began to complain of headaches and sore throats.

The employees quickly began to feel better after they left the building, said Surrey assistant fire chief Joe Deluca.

The substance was released after an automated trash mover shifted garbage around, causing the leak, said Deluca.

"Either it broke a container or there was a substance in a box, we don't know at this point," he said. "The movement of the trash caused the vapours to release into the atmosphere."

Deluca said the hazardous materials team would enter the plant to try to determine what kind of gas escaped.