A US trade panel on Friday narrowly approved a Commerce Department investigation into charges Chinese companies are selling oil well drill pipe in the United States at unfairly low prices.

The US International Trade Commission voted 3-3 that there was a reasonable indication US producers were threatened with injury by the imports.

The tie vote was enough for the Commerce Department to continue an investigation that began last month in response to a petition filed by the United Steelworkers union and companies in Texas and Illinois.

Trade lawyers expect a steady stream of cases against China this year because of an expected increase in imports as the United States recovers from its worst recession in decades.

The United States already has 82 antidumping duty orders in place against a variety of Chinese goods and another 12 countervailing duty orders.

A spate of high-profile cases last year strained ties.

The latest probe covers heavyweight drill pipe and drill collars of iron or steel used to drill oil wells.

The union and companies accuse their Chinese competitors of selling in the United States at below fair market value and of receiving government subsidies.

They have asked for duties from at least 429 percent to 496 percent. The United States imported $194.6 million of the drill pipe from China in 2008.

The Commerce Department is expected to announce preliminary anti-dumping duties in the case in March and preliminary anti-dumping duties in June.

The close ITC decision on Friday suggests the possibility the panel could reverse itself when it decides later this year on whether to give final approval to duties.

Illinois company TMK IPSCO and Texas companies VAM Drilling USA, Rotary Drilling Tools and Texas Steel Conversions Inc joined the steelworkers in filing the case