Three Chinese people have been charged with manslaughter and other offences over the deaths of at least 21 Chinese migrants who drowned while digging for shellfish in Morecambe Bay, northwest England, British police said.

The trio, two men and a woman, had been interviewed by police after the deaths on February 5, and were re-arrested on Wednesday.

The 21 migrant workers drowned when they were caught by racing tides as they gathered cockles in the famously treacherous shallows of Morecambe Bay.

Police have been investigating whether the dead were illegal immigrants used as cheap labour by "gangmasters" who organise groups of itinerant workers for jobs such as crop-picking or shellfish-collecting.

Lin Liangren, 27, has been charged with manslaughter, conspiracy to pervert the course of justice and "conspiracy to commit facilitation", an offence relating to the organisation of illegal immigrants.

Zhao Qingxiao, 19, faces charges of conspiracy to pervert the course of justice and conspiracy to commit facilitation, while Lin Muyong, 29, is charged with conspiracy of commit facilitation.

Twenty-one bodies have been recovered following the drownings, while police believe two people are still missing and presumed dead.

More charges could follow, said Detective Superintendent Mick Gradwell from Lancashire Police, who is leading the inquiry.

"This does not signal the end of the investigation as a number of other people remain on police bail," he said in a statement.

"Our inquiries into exactly what happened on the night of Thursday, February 5 and events leading up to this tragedy are very much the focus of a detailed criminal investigation."

Source: agencies