Chinese authorities have raised the official death toll in last month’s devastating Henan floods to 302, with at least 50 still missing.

The announcement more than triples the confirmed number of people killed in the floods, which had sat at 99 since Thursday.

At a press conference on Monday, Henan authorities announced 292 people were killed in the provincial capital, Zhengzhou, and 47 were missing, state media reported. Another seven were killed and three still missing in Xinxiang city, while two were killed in Pingdingshan and one in Luohe.

Zhengzhou’s mayor, Hou Hong, said 39 people were found dead in underground car parks, and six had died in the cross-city tunnel – raising the tunnel’s toll from four.

Record-breaking rainstorms hit Henan province in central China in late July, overflowing reservoirs, breaching riverbanks, and overwhelming public transport systems and roads in major cities. In Zhengzhou, more than 600mm of rain, equivalent almost to an average year, fell in just three days.

China routinely experiences flooding in summer, but the impact from the unprecedented deluge was exacerbated by rapid urbanisation, conversion of farmland and the worsening climate crisis, as well as overwhelmed flood mitigation systems.

More than 200mm fell in a two-hour window on one afternoon, flooding the city’s subway system and a cross-city tunnel filled with cars. At least 14 died in the subway when about 500 people were trapped in carriages and platforms, with alarming footage showing the water rising up to people’s necks. While hundreds of cars were trapped in the tunnel, many people were reportedly saved by a retired soldier who swam from car to car getting people out.

According to Chinese authorities, the disaster affected 13 million people, damaged nearly 9,000 homes, and caused 53bn yuan (GBP6bn) of economic losses.

Questions around official transparency have swirled in the weeks since the disaster, amid some citizens struggling to search for or find information about their missing loved ones, online censorship, and serious harassment and threats against foreign journalists reporting that residents had concerns about the response, and that there were questions over the government’s preparation.

Senior government officials were among those accusing journalists of “smearing China” and broadcasting lies about the disaster, with particular hostility towards the BBC.

In the aftermath of the floods, local authorities faced official scrutiny for not stopping the Zhengzhou subway or closing schools, with the central government ordering an investigation and improvements.