At least 51 people have been killed in flash floods sweeping the eastern Spanish region of Valencia following torrential rains on Tuesday that left roads and towns under water, local authorities said on Wednesday.

Dozens of videos shared on social media overnight appeared to show people trapped by the floodwaters, with some climbing into trees to avoid being swept away.

Carlos Mazon, the regional leader of Valencia, told a press conference some people remained isolated in inaccessible locations.

“If (emergency services) have not arrived, it's not due to a lack of means or predisposition, but a problem of access,” Mazon said, adding that reaching certain areas was “absolutely impossible”.

Emergency services in the region urged citizens to avoid any kind of road travel and to follow further updates from official sources.

Trains to the cities of Madrid and Barcelona were canceled due to the flooding, and schools and other essential services were suspended in the worst-hit areas.

Footage shared on social media showed firefighters rescuing trapped drivers amid heavy rain in the town of Alzira and cars stranded in flooded streets.

The UME military unit specialized in rescue operations was deployed in some areas to help local emergency workers.

Spain’s state weather agency AEMET declared a red alert in Valencia, a major citrus-growing region, with some areas such as Turis and Utiel recording 200 mm (7.9 inches) of rainfall.

The death toll appeared to be the worst in Europe from flooding since 2021 when almost 200 people died, mainly in Germany.

Scientists say extreme weather events in the region are becoming more frequent due to climate change. Meteorologists think the warming of the Mediterranean, which increases water evaporation, plays a key role in making torrential rains more severe.