They had scattered before the border police even got there, fleeing their corrugated shacks in a densely-populated slum in Petite-Terre, part of France's Indian Ocean archipelago of Mayotte.
A dozen police ran through dirt-track paths strewn with rubbish and furrowed by the rain, watched by a visiting French parliamentary delegation.
On a normal day, these officers round up between 20 and 35 migrants, most of them Comorans. But today was different.
Alerted by the presence of the VIPs from Paris, men without papers did not wait around.
They fled their flimsy encampments in this neighbourhood of 9,000 people and left their wives and children to fend for themselves.
Situated between Madagascar and Mozambique, the Mayotte archipelago is prosperous relative to neighbouring Comoros, an impoverished and unstable island nation which is one of the poorest countries in the world.
Mayotte was part of the Comoros until they split after a referendum on independence from France in 1974.
Mayotte, comprising two islands, Petite-Terre and Grande-Terre, voted strongly to remain part of France while the rest of the Comoros opted for self-rule.
Defying Comoros' continuing claims over Mayotte, the territory today has the administrative status of a French "department," roughly equivalent to a county.
This entitles it to support for infrastructure, medical care, and education just as in mainland France. Its citizens, living in the farthest region of the European Union, have unfettered rights to travel, work and live in the EU.
But one outcome has been a growing migrant crisis.
Thousands of Comorans have been making the 70-kilometre (43-mile) crossing to Mayotte in search of a better future.
The influx prompted a six-week-long wave of strikes and protests this year. Many on Mayotte, home to 250,000 people, blame uncontrolled migration for spiralling crime and increasing demands on public health services.
According to the chief of police, foreigners account for nearly 42 percent of Mayotte's total population and more than half of them are illegal.
- Some help, others hinder -
As the police pushed their way through scrap metal doors into the tiny homes of the island's poorest, one resident pointed them towards an area where she thought some migrants might be hiding.
"There are a lot of people who rat on them," confided a member of the border police operations support group, a 44-person unit.
"Sometimes, when we turn up in a car, people come out to find us."
Others, though, help the migrants flee, like the children who act as spotters and start yelling "moro, moro" -- the equivalent of "fire, fire!" -- to warn that the police are on their way, another officer said.
"These areas are difficult to reach... it's quite dangerous" for the officers, said Julien Kerdoncuf, the deputy prefect in charge of illegal migration.
A policeman agreed. "People often resist (arrest)," he told AFP, saying a colleague had been injured the day before.
- 'Kwassa' crossing -
Police and gendarmes pick up between 50 and 60 migrants every day, roughly half the number that are turned away daily at the border.
With two-thirds detained on land, the others are caught at sea, usually aboard makeshift boats called kwassas.
"There are three types of kwassas," explained Kerdoncuf.
There is the VIP version for two or three passengers, which are "fast and more expensive", low-cost kwassas which can carry 30-40 passengers, and then there are "medical" vessels filled with sick Comorans hoping to get treatment in Mayotte.
To fight illegal immigration at sea, the island has two speedboats and four interceptor vessels. Two more are due to join the fleet in November.
Since mid-March, the authorities have stepped up checks, issuing more than 13,000 expulsion orders, he said.
On Monday, the foreign ministers of France and Comoros met again in a bid to resolve a diplomatic spat.
In March, the Comoros refused to take back nationals expelled from Mayotte; Paris in turn stopped issuing visas to Comorans wishing to travel to France.
French Interior Minister Gerard Collomb said in early September that the Comoran authorities had started taking in some of those turned away from Mayotte "but only in relatively small numbers."
© 2018 AFP