A car carrying British religious volunteers has crashed in northern Romania, killing the driver and injuring three passengers, one critically.

The victims were part of Christian organisation the Grassroots Trust and had been in the country for just a day, according to the trust’s Facebook page.

A 17-year-old boy and his father were said to be among the casualties, having travelled to build houses for poverty-stricken locals.

The Surrey-based organisation said it learned of the crash “with great sadness”, adding: “We extend our deepest sympathy to all affected and thank you for your prayers and support.”

One well-wisher wrote on Facebook: “Praying for you all, that the Lord will hold you tight as you endure what needs to be done in the midst of this tragedy.”

The driver, a man in his 50s, lost control on a “dangerous” stretch of road before slamming into a tree, Marius Rus, an emergency services spokesman in Bistrita Nasaud county, told the Press Association.

One man was severely injured in the crash and airlifted to a major trauma unit hospital after fire crews pulled three trapped passengers from the wreck. He remains in intensive care.

The other two were initially said to be in a stable condition.

The accident happened at about 8.30am (6.30am BST) on Thursday morning near the village of Saratel.

Images posted online by trust director Hugo Anson on Wednesday showed mounds of bricks and cement mixers at a site where the group planned to build two houses.

Rus said: “The road there is very dangerous and people need to slow down a lot. I believe he didn’t know that area was very dangerous.”

He said there was a “small hill” near a railway crossing meaning the car may have jumped if travelling too quickly.

A second carload of volunteers travelling behind suffered shock and panic attacks, he added.

The Grassroots Trust said they were travelling back to the UK and that next of kin had been informed.