Toy giant Lego has scrapped plans to make its bricks from recycled bottles, in a blow to its efforts to cut carbon emissions.
The company said in 2021 that it aimed to produce bricks not containing crude oil within two years.
But on Monday, it said it had found that using the new material didn't reduce carbon emissions.
Lego said it remains "fully committed" to making bricks from sustainable materials.
Lego makes about 4,400 different bricks. Currently, many of them are made using acrylonitrile butadiene styrene (ABS), a virgin plastic made from crude oil.
The move, which was first reported in the the Financial Times, will be seen as a setback after a high-profile push by Lego to improve its green credentials.
Like many other companies, Lego has been exploring alternative materials to plastic as sustainability becomes more important to customers.
One of the challenges has been finding a material that is durable enough to last for generations.
In 2021, it said it had developed prototype bricks made from polyethylene terephthalate (PET) bottles, with some other chemicals added.
The hope was that material could have offered an alternative to oil-based bricks.
But Lego has now revealed that after more than two years of testing, it had found that using recycled PET didn't reduce carbon emissions.
It said the reason for that was because extra steps were required in the production process, which meant it needed to use more energy.
As a result, it said it has "decided not to progress" with making bricks from the material.
It said it was currently testing and developing bricks made from "a range of alternative sustainable materials".
Niels Christiansen, chief executive of Lego, told the FT that there was no "magic material" to resolve the firm's sustainability challenges.
"We tested hundreds and hundreds of materials. It's just not been possible to find a material like that," he said.
A spokesperson for the company told the BBC: "We remain fully committed to making Lego bricks from sustainable materials by 2032.
"We are investing more than $1.2bn in sustainability initiatives in the four years to 2025 as part of our efforts to transition to more sustainable materials and reduce our carbon emissions by 37% by 2032."
