Mobile taxi app Uber says it has increased its size by 50% since it launched in Belfast last month. But Uber would not say how many drivers it currently has working for it in Belfast, or how many fares it had completed.
The US-owned firm said when Uber launches in a new city "it always takes a bit of time to match the supply of cars to rider demand".
Uber is a taxi-booking app for mobile phones which allows customers to locate the nearest cab using the satellite Global Positioning System (GPS), before dispatching it.
Many users have found it difficult to get a cab at busier times, due to the small numbers of drivers signed up to the firm since its launch on December 11.
But the firm's general manager in Belfast, Kieran Harte, said it now takes "just 4.5 minutes" for a taxi to arrive.
The service also operates in Dublin, across the UK, and in around 70 other countries, with drivers fully licensed according to each individual nation's laws.
They can then choose their own hours, with Uber taking around 20% of the total fare.
It comes a year after this paper revealed the $50bn (£34bn) international taxi giant was eyeing up Belfast as its latest business target.
"We're delighted with how well things are progressing in Belfast," said Mr Harte.
"When Uber launches in a new city it always takes a bit of time to match the supply of cars to rider demand.
"However, Uber is already over 50% bigger now than it was in December.
"This is great for customers as the average time from pressing the button to the car arriving is now down to just 4.5 minutes, and this is decreasing further as more professional drivers choose to partner with Uber." Last month Uber said there are "hundreds of drivers in the pipeline who will be hitting the road in the coming days and weeks".
And as the business grows, its reach here is expected to have a big impact on Northern Ireland's traditional taxi businesses.
That includes the two biggest names in the city - FonaCab and Value Cabs.
William McCausland, who operates FonaCab in Belfast, has described the app company's decision to enter the local market as highly concerning.
"This is a big threat to my business, it's not the wonderful thing people seem to think it is," he said. "You'd be very naive not to take it seriously."
Value Cabs operates around 600 taxis in Belfast, while FonaCab has some 500 vehicles in the city.
Uber's boss in the UK, Jo Bertram, has previously said the company brings "competition to an industry which hasn't been shaken up in years".
The mobile phone app, available on both Android and iPhones, works on a cashless system - with users signing up with a credit card - charged for each journey automatically on arrival at their destination.