An International Paper plant on Lake Champlain began a controversial two-week test of burning old tires for fuel Tuesday.

The company was given a temporary burn permit from New York environmental officials in September despite concerns from officials in Vermont, who said the plant's smokestacks could emit toxic heavy metals and other pollutants that would blow eastward over their state.

Vermont state officials tried unsuccessfully to block the test in federal court.

IP is performing the test to determine whether scrap tire chips could supplement fuel oil and wood scraps to power the plant's boiler. The burn was initially expected to begin Monday, but company spent the day performing baseline tests and briefing environmental officials from New York, Vermont and the federal Environmental Protection Agency.

IP spokeswoman Donna Wadsworth said the chips were slowly being added to the fuel mix Tuesday morning in full compliance with applicable laws and health standards.

"The system is working well and under the watchful eye of the regulators," she said.