A day after the sales website crashed due to overwhelming demand, Via Rail says its $150 passes for unlimited travel across Canada for the month of July are now sold out.

On Thursday, the rail carrier announced that more than 4,000 passes in the promotion had been purchased.

The promotion was launched Tuesday as a way to celebrate Canada's sesquicentennial, and overwhelming demand for the program crashed the website that sold the tickets.

Initially the plan was to offer only 1,867 passes — "to coincide with Canada's birth year," Via said — but due to its popularity, the promotion was extended to more than twice as many people as first planned.

"Visits increased at a dramatic rate, and the site experienced five times the usual volume of traffic, causing the reservation system to crash," Via said in a release Thursday.

After fixing the system so that sales could resume, the rail company announced early Thursday that all passes had been sold in less than 36 hours.

The passes allow young people between the ages of 12 and 25 to have unlimited travel across Canada on Via's rail network. And those 26 and older with a valid International Student Identity Card (ISIC) could also purchase it.

Pass holders can travel coast to coast in economy class but must book using the Escape fare category, which is subject to seat availability.

With files from The Canadian Press