The official said Friday that a customs canine sniffed Heaton's luggage when he arrived at Los Angeles International Airport last Saturday and officers found a small amount of cocaine.
According to The Sun, the substance was detected by a sniffer dog at the airport.
Heaton stars as Jonathan Byers in the Netflix supernatural drama.
But there was still grounds for them to refuse Heaton's entry into the States, apparently, and the actor was soon back on another plane flying to London.
Stranger Things" star Charlie Heaton was deported from the United States over "cocaine bust'.
A source told The Sun that the actor wasn't arrested or charged because he was caught with a "very small amount", which bears the effect that "you will not be allowed into the country".
The Deadline article notes that Netflix has not commented or released a statement on the situation, and Heaton's future on the show has not been addressed.
The 23-year-old, who was reportedly sent back to the United Kingdom, missed the Netflix show's season two premiere party on Thursday night, as his co-stars Millie Bobby Brown and Winona Ryder celebrated the release. "CBP officers treat all worldwide travelers with integrity, respect and professionalism while keeping the highest standards of security".