France Strips 7 Police Officers of Guns After Paris Attack.

LONDON — Seven French police officers have been ordered to hand over their weapons and at least one employee has been suspended after security forces were encouraged to report signs of radicalization in their ranks following the fatal knife attack this month at Paris Police Headquarters, the police chief told lawmakers this week.

In the attack on Oct. 3, a veteran police employee killed four colleagues before he was fatally shot in the fortresslike building’s courtyard. The killings abruptly reawakened France to the threat of terrorism, and led President Emmanuel Macron to urge a return to a “society of vigilance.”

One of the most striking signs of that has been the focus on radicalization within the security forces. Agents have raised more concerns about colleagues’ behavior in the past three weeks than in the previous seven years combined, the police chief, Didier Lallement, told a parliamentary hearing on Wednesday.

Mr. Lallement said 33 reports had been generated, leading to the officers’ being stripped of their weapons, and he had recommended two other officers be suspended. No further information on the cases was immediately available.

The hearing was called in an effort to find out why the attacker, Mickaël Harpon, a 45-year-old computer technician, had not been singled out earlier as a threat.

Mr. Harpon had showed signs of radicalization. After 12 people were killed in 2015 at the satirical newspaper Charlie Hebdo, which had published controversial cartoons about Islam, Mr. Harpon had told a colleague, “Serves them right,” according to a leaked internal police report. But colleagues did not file any formal complaints, and no measures were taken against him.

One of Mr. Harpon’s victims, the deputy head of the police intelligence services, had pleaded that the concerns about him be resolved within his unit, and did not formally report his comments to his managers.

Some lawmakers criticized the police as being lax in flagging radicalization and blamed them for not monitoring Mr. Harpon more closely.

Security experts warned that the authorities needed to strike a balance between increased vigilance and avoiding religious discrimination in a country where suspicions against Muslims have festered, especially since a series of terror attacks in 2015.

“If they systematically flag the smallest events, there will be some abuses,” said Jean-Charles Brisard, president of the Center for the Analysis of Terrorism, a research group based in Paris. Mr. Brisard said the police over all had been alert to radicalization, adding that the headquarters attack had most likely been an isolated case.

And flagging too many things can be counter-productive, said Marwan Muhammad, a statistician and former spokesman for the Collective against Islamophobia in France. “When there are too many so-called weak signals, too much noise, there’s no intelligence anymore,” Mr. Muhammad said.

Mr. Lallement acknowledged to lawmakers that he had never expected a threat to come from within. “During the attack, I myself thought that we were being attacked from the outside,” he said.

The trauma from that day is still palpable when officers walk by the staircases and other spots where their colleagues died, he said.

Eric Poulliat, a lawmaker who was an author of a report this year on radicalization in the public service and who questioned Mr. Lallement on Wednesday, said the surge of reports showed that officers had realized they could be the target of more such “blue on blue” attacks.

Mr. Poulliat’s report found that of 150,000 police officers nationwide, 28 were being monitored for suspicious activities as of June.

“They thought they could deal with it on their own,” Mr. Poulliat said about Paris police officers. “They would tell themselves, ‘We can’t have a terrorist within our ranks,’ but now the fear is here.”

A few days after the attack, Mr. Lallement asked officers to be more alert to changes in clothing, appearance and behavior that could signal radicalization. At a ceremony for the victims of the knife attack, Mr. Macron had urged similar vigilance, saying people should be “on the lookout at school, at work, in places of worship, close to home” for “little gestures” and signs of radicalization.

Some lawmakers have suggested that a conversion to Islam could be one of those signs. On Wednesday, two of them asked Mr. Lallement if all recent converts within the police should be monitored.

Mr. Lallement said that a conversion to Islam should not automatically lead to a “systematic denunciation.”

“That’s not how we proceed,” he said.

France Strips 7 Police Officers of Guns After Paris Attack