President Mutharika has promised to take crackdown on corruption

The witness, a government official named Peter Mulamba, disappeared at the weekend.

On Tuesday, a newspaper quoted a minister as saying that Mr Mulamba's body had been found, but the police then said they were still searching for him.

The minister then told MPs he was not sure whether the man was alive or dead.

Since taking office in May, President Bingu wa Mutharika has promised to crackdown on corruption.

The pending trials centre on alleged frauds at Malawi's grain marketing board and a state-run bus company.

Home Affairs Minister Uladi Mussa told The Nation, Malawi's leading daily newspaper, that Mr Mulamba was believed to have killed himself.

At the moment I am not sure whether Mr Mulamba is dead or alive Home Affairs Minister Uladi Mussa

The minister said Mr Mulamba made several telephone calls to his former wife and a number of his relatives "just before he went missing" asking them to take care of his children when he is gone.

But police issued a statement contradicting the minister, saying the search for Mr Mulamba - a former deputy head of the grain marketing board - was still on.

"We haven't found any body," said police spokesman Willy Mwaluka.

Rumours

This prompted opposition MPs to urge Mr Mussa to clarify his position and he told parliament that all he had were rumours.

This is a very serious issue and must be treated as such MP Joseph Njobvuyalema

"At the moment I am not sure whether Mr Mulamba is dead or alive," he said.

MP Joseph Njobvuyalema, of the opposition Malawi Congress Party, said the nation was increasingly becoming impatient and it was irresponsible of the government to issue contradictory statements.

"This is a very serious issue and must be treated as such," he said.

The BBC's Raphael Tenthani in Malawi says all hell broke loose as Mr Mussa was shouted down by opposition MPs as he was trying to justify his position.

He says that Speaker Rodwell Munyenyembe had to intervene to save the minister, saying MPs have to give the minister time to get an official report on the search from police officers on the ground.