Paris ? Four suspected Islamic militants who had an unidentified liquid and an anti-contamination suit were probably planning an attack, France’s interior minister said Tuesday, and media reports linked the men to a terror suspect with alleged ties to al-Qaida.

French counterterrorism agents arrested the men — three Algerians and a Moroccan — Monday in a raid on an apartment in a tough Paris suburb. Agents also seized $5,000 in cash, a computer and extremist Islamic documents, judicial officials said, speaking on condition of anonymity.

Interior Minister Nicolas Sarkozy said the raid also turned up false identity papers, two vials of an undetermined liquid and “a protective military suit against biological, chemical and nuclear risks.” Specialists were studying the vials’ contents.

Sarkozy said the suspects were thought to have spent time in training camps in Afghanistan and Chechnya, and that they had been in contact with Rabah Kadre who was arrested with two other suspects last month in Britain on terrorism-related charges.

Kadre, 35, is accused of possessing materials for the “preparation, instigation or commission” of terrorism. According to French news reports, he has links to the al-Qaida network and had been to terrorist training camps in Afghanistan.

Sarkozy indicated the suspects were planning an attack, saying that “with these four men it was better to arrest them before rather than after.” He did not elaborate.

The men were preparing a chemical attack, according to radio and television reports and the daily newspaper Le Parisien, which quoted unidentified police officials and agents from the counterintelligence service DST. Radio and television reports said the chemicals could be used to pollute public drinking water systems.

But judicial officials told The Associated Press that laboratory tests to determine the exact nature of the substances hadn’t been completed.

France’s top anti-terrorist judge, Jean-Louis Bruguiere, ordered the arrests. He has broad powers to pursue suspects, search their homes, arrest, interrogate and charge them.

Bruguiere has recently stepped up the arrests amid mounting concerns in Europe that a terror attack may be imminent. More than 20 suspects have been taken into custody in five operations since Nov. 24. Eight remain in custody.