PARIS — France’s interior minister announced on Monday plans to open two centers to shelter migrants returning to the northern port city of Calais, determined to get to Britain despite the closing of a vast makeshift camp last fall.

While Gerard Collomb put the number of migrants in Calais at some 400, he said more than 30,000 attempts have been made to sneak into the ferry port, the Eurotunnel train station or jump onto trucks heading to Britain since the start of the year.

The minister also ordered a report looking into claims of police mistreatment of migrants after Human Rights Watch alleged police “routinely” use pepper spray on refugees, including when they were sleeping, and appealed for witnesses to come forward.

Calais, which housed a sprawling, slum-like camp for up to 7,000 refugees and asylum-seekers until it closed in October, has refused to host similar camps. Most of the camp’s inhabitants have been bussed to centers around France.

“We don’t want to restart the bad experiences of the past that all ended in the same way,” Collomb said.

Collomb and the city of Calais appealed a court ruling last month ordering that the hundreds of migrants still making their way to Calais should have access to drinking water, showers and toilets.

The Council of State, France’s highest administrative body, rejected that appeal, ruling Monday that Calais authorities were exposing the migrants to “inhuman or degrading treatment” that amounts to a “grave and manifestly illegal attack on a fundamental freedom.” The body upheld a court order that authorities must help migrants who wish to move to shelters.

In response, Collomb said two centers will be created to shelter willing migrants and speed up assessments of their situations — including whether they must be expelled from France.

In keeping with the court order, he said that officials would set up “mobile sites” to access water and toilets for migrants.

Speaking at a news conference, he said there were 350 to 400 migrants in the area — two-thirds of them Eritreans and Ethiopians, and the rest Afghans and Pakistanis. Aide groups put the figure at up to 700.

The number is small compared to the tens of thousands of migrants who arrive in Italy, the European landing spot for many of those in Calais. But for the French city, guarded by high fences and hundreds of riot police, it is a sign more migrants will arrive if not dissuaded.

Fights among migrants since April have left 38 injured, two of them police, Clomb said.

He refuted claims in a report by Human Rights Watch that riot police patrolling in Calais were pepper-spraying migrants, in part by saying that French security forces use only tear gas — not pepper spray.

However, he said such claims are taken seriously, noting that 23 investigations of alleged police abuse have been opened. He said witnesses should come forward, because abuse claims are often “anonymous, not dated and not localized.”