Bus Eireann and the Garda are carrying out separate investigations into the bus crash outside Frenchpark, Co Roscommon, at the weekend.
Nine of the 45 people on board the Ballina-Dublin bus were still in Roscommon County Hospital yesterday but all are expected to be released soon.
Some 13 of the 42 people taken to hospital were kept in over the weekend with facial and back injuries, cuts and abrasions.
Two women with facial injuries were transferred to University College Hospital, Galway.
Among the passengers were five Czech nationals, including a mother and son. Three of them work as butchers in a meat plant in Ballaghaderreen, Co Roscommon, and were returning home for a fortnight's holiday.
Mr Rojsafnt Rene and Mr Petra Baustein were able to continue their journey, but expressed concern about a colleague who was detained in hospital with head and abdominal injuries for further treatment.
"I have to say that mobile phones are great, irrespective of what I had to say about young people using them in the past," Mr Michael McNeely said.
His son had been able to phone his parents on his cellular phone to reassure them after the accident.
Bus Eireann said it could not determine the cause of the crash, which occurred about 8.40 a.m. on Saturday. The 7.15 a.m. coach from Ballina to Dublin left the road at Leggatinty, just outside French park, and hit a tree. The vehicle then overturned. The road was greasy after overnight rain and morning drizzle, according to Bus Eireann.
No other vehicle is believed to have been involved.
The driver of the bus had only minor injuries, but all the passengers were suffering from shock.
The Western Health Board's emergency plan was activated immediately, and a fleet of ambulances from Boyle and Castlebar, along with a minibus and an Army vehicle, took most of the passengers directly to Roscommon County Hospital.
One man walked away from the scene, and two people were taken to Sligo, according to Mr Kenneth Bryan, Bus Eireann area manager.