Uber is apparently experiencing problems with its mobile app, according to hundreds of complaints from frustrated users.

Users of the ride-hailing app flooded Twitter on Monday with messages that the app was malfunctioning. Some complained about being charged for rides they didn't take and wondered it the app had been hacked. Some users also reported problems with UberEats, the company's food delivery service.

It isn't immediately clear what's causing the problems or how widespread they are. Uber didn't immediately respond to a request for comment but said it in a tweet that it's working to resolve the issue

"We're sorry for the trouble," Uber Support said in a tweet to users. "Our team is looking into this and working to resolve. ASAP."