A Brazilian court has acquitted nine police sergeants for their role in the massacre of 19 landless peasants six years ago in the northern Amazon state of Para. Tuesday's acquittals came as part of an ongoing trial of 149 policemen involved in the killing.

A court in the Amazon port city of Belem Tuesday acquitted the police sergeants, even though the same jury had earlier this month convicted two police commanders for the same crime. The two had been acquitted in a previous trial in 1999.

The prosecution argued that the sergeants did nothing to stop the massacre which took place in 1996 when police opened fire on about 1,000 landless farm-workers who were blocking a highway in Eldorado do Carajas in Para state. Along with the 19 people killed, 80 others were wounded.

However, the defense argued successfully that it was the police commanders, not the sergeants, who were to blame for the killings. Five of the sergeants said they were not armed.

Last week, Major Jose Maria Oliveira was sentenced to 158 years in prison. His superior, Colonel Mario Pantoja, received a 228-year sentence. Under Brazilian law, however, no prisoner can serve more than 30 years in jail. Both men were allowed to remain free pending appeal.

In all, 149 policemen are being tried in the Belem court for the Eldorado do Carajas massacre which is considered as one of the worst human rights violations in recent Brazilian history.

Human rights groups see the widely publicized trials as a test of the government's willingness to prosecute police accused of human rights violations. The first trial in August 1999 led to the acquital of three police commanders for insufficient evidence. But the verdict was later overturned following a domestic and international outcry, and a new trial was ordered.