New York CNN Business  — 

Tesla (TSLA) has expanded its “full self-driving” software to roughly 2,000 Tesla (TSLA) owners, but some drivers were revoked access for not paying close enough attention to the road, according to Tesla (TSLA) CEO Elon Musk.

“FSD Beta has now been expanded … we’ve also revoked beta where drivers did not pay sufficient attention to the road, Musk said in a tweet on Friday. “No accidents to date.”

It’s unclear how many drivers were revoked access from the beta software. Tesla did not immediately respond to a request for comment on the number of drivers who lost access to the program.

The beta version of “full self-driving” was released in October of last year. Tesla’s use of the term “full self-driving” has long been controversial, and criticized by autonomous vehicle experts. To most experts, full self-driving means a car in which a person could safely fall asleep behind the wheel. An attentive human driver isn’t needed.

The news comes after reports that a letter was sent in February from the National Transportation Safety Board to the National Highway Traffic Safety calling for stricter requirements on autonomous driving testing on public roads.

CNBC was the first to report the federal agency’s request for updated safety requirements for public roads testing.

In the letter, NTSB Chairman Robert Sumwalt states that Tesla is testing on public roads but with “limited oversight or reporting requirements.”

“Although Tesla includes a disclaimer that ‘currently enabled features require active driver supervision and do not make the vehicle autonomous,’ NHTSA’s hands-off approach to oversight of AV testing poses a potential risk to motorists and other road users,” Sumwalt added.

Earlier this month, Musk tweeted his plans to double the size of Tesla’s beta testing program with version 8.2 and about ten times the number of testers with version 8.3.

He then later added on Friday the software’s “next significant release” will be next month.

“Going with pure vision — not even using radar,” Musk tweeted. “This is the way to real-world AI.”

– CNN’s Matt McFarland contributed to this report.