Phone line keeps beeping

Phone line keeps beeping as if a phone is off the hook but none are. The modem worked fine at first, phone line was normal and microfilters are on properly. When a phone call came in I picked up the phone and beep beep beep over and over. Now every time I pick up any phone in the house it beeps like a phone is off the hook. I disconnected the modem and still every phone beeps when I pick it up. Can't figure it out.