Magistrates in Marseille jailed five people and placed three others under house arrest on Thursday after charging them with multiple counts of forgery, fraud and conspiracy, according to French media reports.

The move is expected to lead to a trial in France, after recent convictions in the UK and the Netherlands.

Court sources told the AFP news agency the charges related to the investigation that opened when vast quantities of horsemeat were found to have been passed as beef across Europe in 2013.

The sources did not reveal the nationalities of those charged, but French media report that two Belgians were among the 26 arrested in an EU-wide police operation last week and one of them is suspected of being the ringleader.

French authorities estimate that between 2010 and 2013, 4 700 horses unfit for human consumption were slaughtered and introduced into the legal food chain, according to the EU's judicial cooperation agency Eurojust. Four hundred horse passports with anomalies were detected in France alone.