Image caption Hurricane Alex flooded large swathes of northern Mexico.

Rescuers looking for flood survivors in northern Mexico have found two girls clinging to the branches of a tree.

The children who are nine and 10 years old were forced to seek refuge there during flooding.

They told rescue workers they had spent almost four days there without food and water.

Police in the northeastern state of Tamaulipas said their parents had drowned.

A group of fishermen who had set up their camp on the banks of a river first spotted the two youngsters and alerted the authorities.

Lizbeth Dalin and her youngster sister, Lesli Dalimel Gaona Trevino, were taken to hospital where they are being treated for insect bites and de-hydration.

Family car washed away

Doctors said the pair were still traumatised by their ordeal but were in a stable condition.

The girls told rescue officials they had last seen their parents on Monday.

Their father apparently attempted to drive the family car over a bridge across the Pilon River but veered off the road into the flooded river.

The vehicle with their parents and two siblings on board was washed away.

So far the authorities have recovered several bodies from the flooded river but have not accounted for one person.

Hurricane plays havoc

"We still haven't found their 15-year-old sister. We'll shortly resume the search for her," said Marisela Cantu, a police spokeswoman.

"We hope we'll also find her alive and well."

Hurricane Alex has caused havoc in Tamaulipas state and the northern region close to the border with the United States.

Torrential rains and heavy floods have killed at least four people in the past two weeks including the latest reported deaths.

Thousands have been left homeless by the tropical storm as it swept across northern Mexico.