It's not clear why the calls are being placed, or if they're coming from iPhones or Apple Watches. Both devices are capable of making phone calls even when unattached to a cellular plan.

The tech giant has been “very responsive,” Jimenez said. “It's been diligently working to resolve the problem.”

Apple said in a statement that it was aware of the problem with 911 calls from its Elk Grove facility. “We take this seriously, and we are working closely with local law enforcement to investigate the cause and ensure this doesn’t continue,” Apple said.

All cellphones are able to make emergency calls even when not part of a calling plan, as long they have a signal and enough charge in their battery. But as part of its safety features, Apple has made it particularly easy to call for emergency services from devices that connect to a cell network.

To trigger an Apple emergency call on the iPhone 8 or iPhone X, someone has to hit buttons on both sides of the phone simultaneously, which lets you choose to place a 911 call without unlocking the phone. Holding the buttons down continuously will prompt a call in five seconds. On older iPhones, you have to hit the power button five times. On the Watch, holding down the side button triggers a similar response. In both cases, a loud whooping noise plays in the few seconds before the device actually makes a call.

The number of accidental 911 calls has been on the rise with the broad adoption of smartphones. In 2011, researchers from Google studied 911 calls in San Francisco and found that 30 percent of emergency calls from wireless phones were accidental. That was lower than the percentage for wireline calls, with 37 percent accidental.