The bus was carrying mostly young people going home from work and it crashed during the night when passengers were sleeping.

"People were screaming, begging for help, there were no tools, had we had the tools we might have been able to help somehow," one passenger, identified as Aleksandr, told a local television station.

"We took as many people out as we could."

Earlier, local media and medical services said six people had died in the accident, but the death toll was later revised.

"We know that one person was brought to a hospital in a critical condition. A life-rescuing surgery was conducted and we hope that this life will be saved," the region's governor Ewa Leniart told a news conference, saying 14 of the injured people were in a serious condition.

There were 57 people on the bus, Leniart added.

A local medical spokesman said the bus was bound for Ukraine when the accident took place.

"The passengers were mostly sleeping when the accident happened, most were not strapped with seat belts, so they were seriously injured," the spokesman said.

"They were mostly young people going home from work."

He said the bus had apparently hit a traffic barrier while leaving a highway and careened into the ditch. Police said it was too early to say what might have caused the accident.

All of the passengers were Ukrainians, a fire brigade official told local television.

An estimated one million to two million Ukrainians live or work in Poland.

Australian Associated Press