A car hire firm highlighted in Guardian Money two weeks ago is being investigated by police "in relation to fraud". On 16December we told how adverts had appeared in some national newspapers, including the Times and Metro, promoting 118 Car Hire. They promised "unbeatable" deals on Christmas car hire with a "huge range of cars available", "affordable rates guaranteed", and free delivery and collection.

When we visited the company's premises near Heathrow airport, we were told there was no one there from 118 Car Hire that day, and we could not see any evidence of a fleet of vehicles.

We have since been contacted by several people who handed over money to the company and say they were left with no car. Some say they had more money deducted from their account than they were told would be taken. Complaints have also appeared on MoneySavingExpert.com forums.

The Metropolitan police has now issued a "fraud alert" on its website that names 118 Car Hire. It says it is "investigating 118 Car Hire in relation to fraud. If anyone believes they are a victim – ie, anyone who has paid for a vehicle that has not been delivered or who has had more money taken from their account than expected", they should report it to Action Fraud or telephone 0300 123 2040.

The timing of the Guardian's coverage may have limited the numbers making bookings. A police spokeswoman told Money that "as of just before Christmas" there were more than 30 known victims, and inquiries were continuing. She added: "Action has been taken to ensure others do not fall victim to the fraud."