The scare comes a year after the dioxin crisis which forced the wholesale destruction of meat and dairy products in Belgium.
The government said that any food which might have come from animals fed with the suspect feed would be removed from the food chain and destroyed.
"It's lucky that we picked up on the contamination as early as we did, thanks to our testing programme," Agriculture Minister Jaak Gabriels said.
High levels of toxic polychlorinated biphenyls (PCBs) - up to 925 times the legal norm - were found in animal feed manufactured by the Bauduin-Cambier company in the town of Feluy, 40km (25 miles) south of Brussels.
Mr Gabriels said 205 farms which took fodder from Bauduin-Cambier were being checked.
Dioxins
Last May food products across Belgium were recalled after cancer-causing dioxins entered
the food chain via animal feed made with contaminated fats.
Shop shelves were stripped bare and countries around the world banned imports of Belgian food products.
PCBs have a similar effect on human health as dioxins.
A spokesman for Bauduin-Cambier said the company suspected PCBs found in its feed may have originated in insecticides.
Rapid response
Following last year's scandal, Belgium instituted a series of control mechanisms to avoid a repeat of the damaging crisis, and the government said it had carried out some 3,000 tests on fodder companies over the past 12 months.
The government said the European Commission had been informed of the situation.
The Commission, the executive of the European Union, operates an early warning system to inform all EU states of potential food health problems.
In last year's crisis, Belgium was criticised for being slow to provide information about the contamination.