Almost all of the 25,100 tonnes of defective milk powder seized in the 2008 toxic baby food probe had been incinerated and buried, and none had been found to have re-entered the market, China's National Food Safety Rectification Office said Monday.

Only a small amount of tainted milk powder was kept for specific purposes, such as for evidence in judicial procedures, an official with the office said.

The milk powder destroyed was sealed by local authorities or quality supervision and inspection administrative organs in 2008, who suspected it was contaminated or likely to be tainted with melamine, the office said.

After a nationwide crackdown against the "toxic milk powder" in 2008,some melamine-tainted dairy products had resurfaced in several Chinese provinces in 2009.

The office had urged local authorities to launch another special investigation from February 1 to 10 to ascertain the precise amount of tainted milk powder and to seal it immediately upon discovery.

Three executives of Shanghai Panda Dairy Company were jailed for terms of three to five years earlier this month for their roles in the production and sale of melamine-tainted dairy products last year.

In December last year, police detained the general manager and two workers at Shaanxi Jinqiao Dairy Co. Ltd. in connection with tainted milk powder.

The 2008 milk scandal, in which milk laced with melamine led to the deaths of at least six babies and sickened 300,000 others, and resulted in the collapse of the Sanlu dairy group.

China's dairy industry saw a recovery in 2009, when production increased by 12.9 percent, reaching about 19.35 million tonnes.