Apple has not lived up to its commitment to improve working conditions in its Chinese suppliers’ factories, according to a new undercover BBC investigation. In a documentary scheduled to air tonight, titled “Apple’s Broken Promises,” BBC Panorama shows what conditions inside a Chinese iPhone 6 production line are really like. The investigation found standards being breached at Pegatron factories on everything from workers’ hours, to dormitories, to juvenile workers — all areas in which Apple had promised sweeping improvements over the past several years. The documentary includes footage of exhausted workers falling asleep on 12-hour shifts, an undercover reporter who was forced to work 18 days in a row despite repeated requests for time off, and another reporter who worked shifts of up to 16 hours. Panorama also followed Apple’s supply chain down to the Indonesian island of Bangka, and found evidence that tin from illegal mines could be entering Apple’s supply chain, despite the company’s dedication to ethical sourcing of minerals. Investigative reporters also found children digging tin ore out of the mines by hand under extremely dangerous conditions.

Apple declined to be interviewed for the story, but the company did release a statement saying that it is “aware of no other company doing as much as Apple to ensure fair and safe working conditions.” The company noted that it was a “very common practice” for workers to nap during breaks, but that it would “investigate any evidence” of workers falling asleep while actually working. In its statement, the company said that it had monitored the working hours of “more than a million workers” and that the workers at the particular plant in question were averaging 55 hours per week. Responding to the situation in Bangka, Apple described it as a “complex situation” as many miners sell tin through a series of middle men, so it’s not always possible to confirm the sources of tin, but Apple remains engaged in Bangka to attempt to “drive changes on the ground” to improve the situation there.

Panorama: Apple’s Broken Promises airs tonight on BBC One and will be available later on BBC’s iPlayer platform.