911 operators are getting overwhelmed -- by butt dials.

According to a report by The Daily, for every 100 calls made to 911 this year, about 40 were accidental, likely coming from someone's purse or pocket. In total, 100 million "illegitimate 911 calls" were made last year.

The issue of pocket dials tying up the time of emergency responders has already been well documented in large cities. New York City Mayor Michael Bloomberg's administration, for example, released a report last spring that found accidental calls actually outnumbered real emergency calls in which police were dispatched to a scene, the New York Daily News reports.

But The Daily reports that responders are struggling to handle the number of errant dials on a national level. Responders have to stay on the phone even if there's just silence to find out if the call is related to an emergency, which leads to less efficient responses to real emergencies. Industry sources told the news outlet that the surge in calls can be explained by people not locking their phones, having 911 on speed dial or having an emergency call function on their phones.

Visit The Daily for an infographic with more data.

And because so many people have cell phones these days, there's also apparently a growing issue of responders being inundated with calls about the same emergency. A recent Twitter hoax by New Jersey teen falsely claiming an intruder was in her house, for example, produced about 6,000 calls to 911.

Despite the drain that accidental calls place on call centers, "butt dials" have proved useful in catching criminals on occasion.

In August, police were made aware of a drug deal in Scranton, Pa., thanks to a pocket dial from the person buying the drugs, Gawker notes. Similarly, this week in Michigan, two men were arrested for possession of marijuana after police overheard their conversation, Patch reports.

And last spring, a car thief accidentally called 911 and spoke about plans to carry out his crimes, Gizmodo reports. However, he called 911 a total of four times before the police finally caught him.