Hackers claim to have breached Verkada, a security company that provides cameras to companies including Tesla.
Bloomberg reported feeds from prisons, psychiatric hospitals, clinics, and Verkada's own offices were hijacked.
Verkada told the BBC it was "investigating the scale and scope of this issue".
The company added it had notified law enforcement. However, it did not confirm the size and scale of the attack.
Reuters has also reported that the transport start-up Virgin Hyperloop was among the list of impacted user accounts disclosed by the hackers.
Software provider Cloudflare told the BBC that it had been alerted to a "handful" of cameras that might have been compromised at its offices around the world.
A Verkada camera inside a Florida hospital, reportedly seen by Bloomberg, showed what appeared to be eight workers tackling a man and pinning him to a bed.
Another video showed officers in a police station in Stoughton, Massachusetts questioning a man in handcuffs.
One, inside a Tesla warehouse in Shanghai, showed people working on an assembly line.
The BBC has not been able to independently verify these videos.
The hackers also said they had gained access to the security cameras of Sandy Hook Elementary School in Newtown, Connecticut, where a gunman killed more than 20 people in 2012.
Speaking to Bloomberg, Tille Kottmann claimed credit for hacking into Verkada's systems.
The reasons for the hack, Kottmann said, were, "lots of curiosity, fighting for freedom of information and against intellectual property, a huge dose of anti-capitalism, a hint of anarchism - and it's also just too much fun not to do it".
The attack was reportedly unsophisticated, involving use of a "super admin" account to gain access to Verkada.
Bloomberg said that after they had contacted Verkada, the hackers lost access to the video feeds and archives.
A spokesperson for Verkada told the BBC: "We have disabled all internal administrator accounts to prevent any unauthorised access.
"Our internal security team and external security firm are investigating the scale and scope of this issue, and we have notified law enforcement."
The company has also set up a support line for their customers.
Meanwhile Cloudflare told the BBC: "This afternoon we were alerted that the Verkada security camera system that monitors main entry points and main thoroughfares in a handful of Cloudflare offices may have been compromised.
"The cameras were located in a handful of offices that have been officially closed for several months."
Tesla has yet to comment.
The breach comes after further details of a hack on Microsoft Exchange are beginning to emerge.
The attack used previously unknown flaws in the email software - and sometimes stolen passwords - to steal data from targets' networks.
If you really look closely, most overnight successes took a long time.