Twelve police officers in France\'s crime-ridden Marseille appeared in court Friday on suspicion of corruption, extortion and drug dealing, with a prosecutor claiming there was \"overwhelming\" proof of guilt. Seven were locked up and five granted provisional release while French Interior Minister Manuel Valls announced he was suspending them and terminating their anti-criminal brigade team. \"The deeds for which they are being pursued are exceptionally grave\", the interior ministry said in a statement, and if they proved true they \"would damage the honour and the probity that must be shown by those who guarantee the security of our fellow citizens.\" Cannabis and money had been found in the lockers of the members of an elite detective squad and above a false ceiling in their office building in the northern district of the southern French city, prosecutor Jacques Dallest said. The officers were arrested on Tuesday. They are suspected of having stolen drugs and cash from dealers and of holding on to cigarettes confiscated from illicit sellers. Dallest said secretly recorded conversations in their official vehicles were \"very revealing\" and suggested the alleged corruption could have involved more officers than those in court on Friday. \"The feeling is that gangrene has taken hold of this service,\" the prosecutor said. In Paris, Interior Minister Valls said the officers would face harsh punishment if charged and found guilty. \"If the allegations against them are proven, I will be extremely harsh and will take decisions,\" he said, adding there is \"no place for those who dirty the uniforms of the police.\" If charges are brought, the Marseille affair will be the second major corruption case to hit the French police in little over a year. Michel Neyret, the former deputy police chief of Lyon who was hailed for cutting drug crime and jewellery heists, is currently under house arrest awaiting trial on charges of accepting gifts and favours from members of the city\'s underworld. French Prime Minister Jean-Marc Ayrault last month announced beefed up security with 205 extra police to tackle deadly gang violence in Marseille following a wave of underworld shootings. He also announced the creation of a new security zone in the city\'s southern quarters. The Mediterranean port of some 850,000 residents, long known as a hotbed of crime, has been struck by a wave of shootings with assault rifles in turf wars over the lucrative illegal drug trade. A district mayor had urged the government to take drastic steps, even appealing for the army to be sent in, but the call was rejected quickly by Valls.