Northumbria Police said officers were investigating allegations of fraud in relation to South Shields Day Trips, which arranges visits to theme parks.
The force has received 200 complaints and all trips have now been halted.
Those affected are being urged to attend a meeting at Chuter Ede school, Galsworthy Road, on 11 August.
A 24-year-old woman has been arrested on suspicion of fraud and bailed.
Det Insp Paul Stewart, who is leading the investigation, said: "We have now made contact with all customers, however, due the volume have not yet taken information from all of them and I would urge any customers who have not yet been spoken to by police to attend the meeting between 5pm and 9pm.
"If they cannot attend we will make contact with them in due course but would ask they are patient."
A meeting is being held for the potential victims of a day trip Facebook page at the centre of a fraud probe.