Plaintiffs who won a $18 billion US pollution judgment against Chevron Corp. in Ecuador say they've begun their campaign to collect the money, filing suit against the company in Canada.

Plaintiffs' lawyer Pablo Fajardo says the case filed in an Ontario court Wednesday is the first in a series of lawsuits planned for 30 countries on four continents where Chevron has assets.

San Ramon, Calif.-based Chevron maintains the Ecuador judgment is fraudulent, alleging it resulted from bribery.

The ruling stems from contamination in Ecuador's Amazon region between 1972 and 1990 by Texaco, which Chevron bought in 2001. Chevron contends Texaco fully remediated its share of environmental damage before leaving Ecuador in 1992.