More people have died crossing the border from Mexico to the US in the first seven months of 2017 compared to the year before, even though significantly fewer people seem to be attempting the journey, according to the United Nation’s migration agency.

The number of migrant deaths tallied at the border jumped 17% from 204 in the first seven months of 2016 to 232 migrant fatalities in 2017, the International Organization for Migration (IOM) said.

Meanwhile, the US Border Patrol has reported that about half as many migrants were apprehended during border crossings in the first six months of 2016 compared to the first six months of 2017 – down from 267,746 people to 140,024 people.

Adam Isacson, senior associate for defense oversight at the Washington Office on Latin America, said the increase was shocking because of the drop in apprehensions, which indicate fewer people migrating overall. “The ratio to people dying to people trying has to be way higher than 17%,” Isacson told the Guardian.

The report does not identify what could be causing the change, but historically, stricter immigration policies in the US have driven people to take more dangerous routes. This is partially because these policies don’t mitigate the factors that drive people to leave, such as the threat of gang violence, crime and lack of economic opportunity.

July saw the highest number of deaths of any month this year, with 50 bodies discovered, including those of the 10 people who died while being smuggled across the border in a sweltering 18-wheel truck. Days later, at least four people, including two children, died trying to cross the Rio Grande.

Isacson said people in Texas are also reporting an especially hot summer, which would cause more dangerous border crossing conditions, and that it was possible increasing violence in border towns could have an impact on the fatality rate.

There is also a concern that more women and children could be attempting more dangerous border crossings, instead of seeking asylum, because of a reported uptick in cases in which immigration officials have illegally turned back asylum seekers at the southern border since Trump was elected in November 2016.

A lawsuit filed last month accuses US border officials of putting asylum seekers in danger by systemically threatening, misleading or rejecting them.

“It would be a nightmare if you have more women and children among those [fatalities] – hopefully that is just a hypothesis that is completely way out there and wrong,” Isacson said.

The IOM report notes that the fatality calculation is likely to be an underestimate because migrant fatalities often occur while people are crossing a vast, remote desert or a large, swift body of water.